Reorganize modules 🧱

26 files changed, 515 insertions, 550 deletions

diff --git a/src/error.rs b/src/error.rs
index b3597266..cd107741 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -1,5 +1,5 @@
 use serde::Serialize;
-use crate::syntax::SpanVec;
+use crate::syntax::span::SpanVec;
 
 
 pub type Errors = SpanVec<Error>;
@@ -10,14 +10,14 @@ pub struct Error {
     pub severity: Severity,
 }
 
-impl Error {
-    pub fn new(message: impl Into<String>, severity: Severity) -> Error {
-        Error { message: message.into(), severity }
-    }
-}
-
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Serialize)]
 pub enum Severity {
     Warning,
     Error,
 }
+
+impl Error {
+    pub fn new(message: impl Into<String>, severity: Severity) -> Error {
+        Error { message: message.into(), severity }
+    }
+}
diff --git a/src/export/pdf.rs b/src/export/pdf.rs
index c4020e10..421ffb19 100644
--- a/src/export/pdf.rs
+++ b/src/export/pdf.rs
@@ -8,7 +8,7 @@ use tide::content::Content;
 use tide::doc::{Catalog, Page, PageTree, Resource, Text};
 use tide::font::{
     CIDFont, CIDFontType, CIDSystemInfo, FontDescriptor, FontFlags, Type0Font,
-    CMap, CMapEncoding, FontStream, GlyphUnit, WidthRecord
+    CMap, CMapEncoding, FontStream, GlyphUnit, WidthRecord,
 };
 
 use toddle::Error as FontError;
@@ -16,7 +16,7 @@ use toddle::font::OwnedFont;
 use toddle::query::{SharedFontLoader, FontIndex};
 use toddle::tables::{
     CharMap, Header, HorizontalMetrics, MacStyleFlags,
-    Name, NameEntry, Post, OS2
+    Name, NameEntry, Post, OS2,
 };
 
 use crate::layout::{MultiLayout, Layout, LayoutAction};
diff --git a/src/func/macros.rs b/src/func.rs
index 764f0836..a7cdfe2f 100644
--- a/src/func/macros.rs
+++ b/src/func.rs
@@ -1,5 +1,35 @@
 //! Helper types and macros for creating custom functions.
 
+use crate::syntax::{ParseContext, Parsed};
+use crate::syntax::func::FuncHeader;
+use crate::syntax::span::Spanned;
+
+pub mod prelude {
+    pub use crate::layout::prelude::*;
+    pub use crate::layout::{LayoutContext, Commands, layout};
+    pub use crate::layout::Command::{self, *};
+    pub use crate::style::{LayoutStyle, PageStyle, TextStyle};
+    pub use crate::syntax::SyntaxModel;
+    pub use crate::syntax::expr::*;
+    pub use crate::syntax::func::*;
+    pub use crate::syntax::func::keys::*;
+    pub use crate::syntax::func::values::*;
+    pub use crate::syntax::span::{Span, Spanned};
+}
+
+
+/// Parse a function from source code.
+pub trait ParseFunc {
+    type Meta: Clone;
+
+    /// Parse the header and body into this function given a context.
+    fn parse(
+        header: FuncHeader,
+        body: Option<Spanned<&str>>,
+        ctx: ParseContext,
+        metadata: Self::Meta,
+    ) -> Parsed<Self> where Self: Sized;
+}
 
 #[macro_export]
 macro_rules! function {
@@ -35,15 +65,15 @@ macro_rules! function {
         $decos:ident,
         $metadata:ident
     ) $code:block $($r:tt)*) => {
-        impl $crate::func::Parse for $name {
+        impl $crate::func::ParseFunc for $name {
             type Meta = $meta;
 
             fn parse(
-                #[allow(unused)] mut header: FuncHeader,
-                #[allow(unused)] $body: Option<Spanned<&str>>,
-                #[allow(unused)] $ctx: ParseContext,
+                #[allow(unused)] mut header: $crate::syntax::func::FuncHeader,
+                #[allow(unused)] $body: Option<$crate::syntax::span::Spanned<&str>>,
+                #[allow(unused)] $ctx: $crate::syntax::ParseContext,
                 #[allow(unused)] $metadata: Self::Meta,
-            ) -> Parsed<Self> where Self: Sized {
+            ) -> $crate::syntax::Parsed<Self> where Self: Sized {
                 let mut errors = vec![];
                 let mut decorations = vec![];
                 #[allow(unused)] let $header = &mut header;
@@ -67,8 +97,9 @@ macro_rules! function {
             fn layout<'a, 'b, 'c, 't>(
                 #[allow(unused)] &'a $this,
                 #[allow(unused)] mut $ctx: $crate::layout::LayoutContext<'b, 'c>,
-            ) -> $crate::syntax::DynFuture<'t, $crate::layout::Layouted<$crate::func::Commands<'a>>>
-            where
+            ) -> $crate::layout::DynFuture<'t, $crate::layout::Layouted<
+                $crate::layout::Commands<'a>>
+            > where
                 'a: 't,
                 'b: 't,
                 'c: 't,
@@ -96,7 +127,7 @@ macro_rules! body {
             // Since the body span starts at the opening bracket of the body, we
             // need to add 1 column to find out the start position of body
             // content.
-            let start = body.span.start + Position::new(0, 1);
+            let start = body.span.start + $crate::syntax::span::Position::new(0, 1);
             let parsed = $crate::syntax::parse(start, body.v, $ctx);
             $errors.extend(parsed.errors);
             $decos.extend(parsed.decorations);
@@ -122,7 +153,7 @@ macro_rules! body {
 #[macro_export]
 macro_rules! err {
     (@$severity:ident: $span:expr; $($args:tt)*) => {
-        $crate::syntax::Spanned { v: err!(@Error: $($args)*), span: $span }
+        $crate::syntax::span::Spanned { v: err!(@Error: $($args)*), span: $span }
     };
 
     (@$severity:ident: $($args:tt)*) => {
diff --git a/src/layout/actions.rs b/src/layout/actions.rs
index 1bf5d684..710d92b4 100644
--- a/src/layout/actions.rs
+++ b/src/layout/actions.rs
@@ -1,10 +1,12 @@
 //! Drawing and cofiguration actions composing layouts.
 
+use std::io::{self, Write};
 use std::fmt::{self, Display, Formatter};
 use toddle::query::FontIndex;
 
-use super::*;
-use LayoutAction::*;
+use crate::size::{Size, Size2D};
+use super::{Layout, Serialize};
+use self::LayoutAction::*;
 
 
 /// A layouting action.
diff --git a/src/layout/line.rs b/src/layout/line.rs
index f7777ae0..5e0839b1 100644
--- a/src/layout/line.rs
+++ b/src/layout/line.rs
@@ -1,3 +1,4 @@
+use super::stack::{StackLayouter, StackContext};
 use super::*;
 
 
diff --git a/src/layout/mod.rs b/src/layout/mod.rs
index 209874a1..f8074524 100644
--- a/src/layout/mod.rs
+++ b/src/layout/mod.rs
@@ -3,40 +3,26 @@
 use std::io::{self, Write};
 use std::fmt::{self, Display, Formatter};
 use smallvec::SmallVec;
-use toddle::query::{SharedFontLoader, FontIndex};
+use toddle::query::FontIndex;
 
-use crate::error::Errors;
-use crate::syntax::{SyntaxModel, SpanVec};
 use crate::size::{Size, Size2D, SizeBox};
-use crate::style::LayoutStyle;
+use self::{GenericAxis::*, SpecificAxis::*, Direction::*, Alignment::*};
 
-mod actions;
-mod model;
-mod line;
-mod stack;
-mod text;
+pub mod line;
+pub mod stack;
+pub mod text;
 
-/// Common types for layouting.
-pub mod prelude {
-    pub use super::*;
-    pub use GenericAxis::*;
-    pub use SpecificAxis::*;
-    pub use Direction::*;
-    pub use Alignment::*;
-}
+pub_use_mod!(actions);
+pub_use_mod!(model);
 
-/// Different kinds of layouters (fully re-exported).
-pub mod layouters {
-    pub use super::model::ModelLayouter;
-    pub use super::line::{LineLayouter, LineContext};
-    pub use super::stack::{StackLayouter, StackContext};
-    pub use super::text::{layout_text, TextContext};
+pub mod prelude {
+    pub use super::{LayoutSpace, LayoutExpansion, LayoutAxes, LayoutAlignment};
+    pub use super::GenericAxis::{self, *};
+    pub use super::SpecificAxis::{self, *};
+    pub use super::Direction::{self, *};
+    pub use super::Alignment::{self, *};
 }
 
-pub use self::actions::{LayoutAction, LayoutActions};
-pub use self::layouters::*;
-pub use self::prelude::*;
-
 
 /// A collection of layouts.
 pub type MultiLayout = Vec<Layout>;
@@ -67,49 +53,32 @@ impl Layout {
     }
 }
 
-/// The general context for layouting.
-#[derive(Debug, Clone)]
-pub struct LayoutContext<'a, 'p> {
-    /// The font loader to retrieve fonts from when typesetting text
-    /// using [`layout_text`].
-    pub loader: &'a SharedFontLoader<'p>,
-    /// The style for pages and text.
-    pub style: &'a LayoutStyle,
-    /// The base unpadded dimensions of this container (for relative sizing).
-    pub base: Size2D,
-    /// The spaces to layout in.
-    pub spaces: LayoutSpaces,
-    /// Whether to have repeated spaces or to use only the first and only once.
-    pub repeat: bool,
-    /// The initial axes along which content is laid out.
-    pub axes: LayoutAxes,
-    /// The alignment of the finished layout.
-    pub alignment: LayoutAlignment,
-    /// Whether the layout that is to be created will be nested in a parent
-    /// container.
-    pub nested: bool,
-    /// Whether to debug render a box around the layout.
-    pub debug: bool,
-}
-
-pub struct Layouted<T> {
-    pub output: T,
-    pub errors: Errors,
+/// Layout components that can be serialized.
+pub trait Serialize {
+    /// Serialize the data structure into an output writable.
+    fn serialize<W: Write>(&self, f: &mut W) -> io::Result<()>;
 }
 
-impl<T> Layouted<T> {
-    pub fn map<F, U>(self, f: F) -> Layouted<U> where F: FnOnce(T) -> U {
-        Layouted {
-            output: f(self.output),
-            errors: self.errors,
+impl Serialize for Layout {
+    fn serialize<W: Write>(&self, f: &mut W) -> io::Result<()> {
+        writeln!(f, "{:.4} {:.4}", self.dimensions.x.to_pt(), self.dimensions.y.to_pt())?;
+        writeln!(f, "{}", self.actions.len())?;
+        for action in &self.actions {
+            action.serialize(f)?;
+            writeln!(f)?;
         }
+        Ok(())
     }
 }
 
-pub async fn layout(model: &SyntaxModel, ctx: LayoutContext<'_, '_>) -> Layouted<MultiLayout> {
-    let mut layouter = ModelLayouter::new(ctx);
-    layouter.layout_syntax_model(model).await;
-    layouter.finish()
+impl Serialize for MultiLayout {
+    fn serialize<W: Write>(&self, f: &mut W) -> io::Result<()> {
+        writeln!(f, "{}", self.len())?;
+        for layout in self {
+            layout.serialize(f)?;
+        }
+        Ok(())
+    }
 }
 
 /// A possibly stack-allocated vector of layout spaces.
@@ -405,31 +374,3 @@ impl LastSpacing {
         }
     }
 }
-
-/// Layout components that can be serialized.
-pub trait Serialize {
-    /// Serialize the data structure into an output writable.
-    fn serialize<W: Write>(&self, f: &mut W) -> io::Result<()>;
-}
-
-impl Serialize for Layout {
-    fn serialize<W: Write>(&self, f: &mut W) -> io::Result<()> {
-        writeln!(f, "{:.4} {:.4}", self.dimensions.x.to_pt(), self.dimensions.y.to_pt())?;
-        writeln!(f, "{}", self.actions.len())?;
-        for action in &self.actions {
-            action.serialize(f)?;
-            writeln!(f)?;
-        }
-        Ok(())
-    }
-}
-
-impl Serialize for MultiLayout {
-    fn serialize<W: Write>(&self, f: &mut W) -> io::Result<()> {
-        writeln!(f, "{}", self.len())?;
-        for layout in self {
-            layout.serialize(f)?;
-        }
-        Ok(())
-    }
-}
diff --git a/src/layout/model.rs b/src/layout/model.rs
index 13d38083..2e61b453 100644
--- a/src/layout/model.rs
+++ b/src/layout/model.rs
@@ -1,9 +1,15 @@
+use std::future::Future;
+use std::pin::Pin;
 use smallvec::smallvec;
+use toddle::query::SharedFontLoader;
 
 use crate::error::Errors;
-use crate::func::Command;
-use crate::syntax::{Model, DynFuture, SyntaxModel, Node};
-use crate::syntax::{SpanVec, Spanned, Span, offset_spans};
+use crate::style::{LayoutStyle, PageStyle, TextStyle};
+use crate::size::{Size, Size2D};
+use crate::syntax::{Model, SyntaxModel, Node};
+use crate::syntax::span::{Spanned, Span, offset_spans};
+use super::line::{LineLayouter, LineContext};
+use super::text::{layout_text, TextContext};
 use super::*;
 
 
@@ -15,6 +21,76 @@ pub struct ModelLayouter<'a, 'p> {
     errors: Errors,
 }
 
+/// The general context for layouting.
+#[derive(Debug, Clone)]
+pub struct LayoutContext<'a, 'p> {
+    /// The font loader to retrieve fonts from when typesetting text
+    /// using [`layout_text`].
+    pub loader: &'a SharedFontLoader<'p>,
+    /// The style for pages and text.
+    pub style: &'a LayoutStyle,
+    /// The base unpadded dimensions of this container (for relative sizing).
+    pub base: Size2D,
+    /// The spaces to layout in.
+    pub spaces: LayoutSpaces,
+    /// Whether to have repeated spaces or to use only the first and only once.
+    pub repeat: bool,
+    /// The initial axes along which content is laid out.
+    pub axes: LayoutAxes,
+    /// The alignment of the finished layout.
+    pub alignment: LayoutAlignment,
+    /// Whether the layout that is to be created will be nested in a parent
+    /// container.
+    pub nested: bool,
+    /// Whether to debug render a box around the layout.
+    pub debug: bool,
+}
+
+pub struct Layouted<T> {
+    pub output: T,
+    pub errors: Errors,
+}
+
+impl<T> Layouted<T> {
+    pub fn map<F, U>(self, f: F) -> Layouted<U> where F: FnOnce(T) -> U {
+        Layouted {
+            output: f(self.output),
+            errors: self.errors,
+        }
+    }
+}
+
+/// A sequence of layouting commands.
+pub type Commands<'a> = Vec<Command<'a>>;
+
+/// Layouting commands from functions to the typesetting engine.
+#[derive(Debug)]
+pub enum Command<'a> {
+    LayoutSyntaxModel(&'a SyntaxModel),
+
+    Add(Layout),
+    AddMultiple(MultiLayout),
+    AddSpacing(Size, SpacingKind, GenericAxis),
+
+    FinishLine,
+    FinishSpace,
+    BreakParagraph,
+    BreakPage,
+
+    SetTextStyle(TextStyle),
+    SetPageStyle(PageStyle),
+    SetAlignment(LayoutAlignment),
+    SetAxes(LayoutAxes),
+}
+
+pub async fn layout(model: &SyntaxModel, ctx: LayoutContext<'_, '_>) -> Layouted<MultiLayout> {
+    let mut layouter = ModelLayouter::new(ctx);
+    layouter.layout_syntax_model(model).await;
+    layouter.finish()
+}
+
+pub type DynFuture<'a, T> = Pin<Box<dyn Future<Output=T> + 'a>>;
+
 impl<'a, 'p> ModelLayouter<'a, 'p> {
     /// Create a new syntax tree layouter.
     pub fn new(ctx: LayoutContext<'a, 'p>) -> ModelLayouter<'a, 'p> {
diff --git a/src/layout/text.rs b/src/layout/text.rs
index 16ae93da..eb598e2f 100644
--- a/src/layout/text.rs
+++ b/src/layout/text.rs
@@ -6,12 +6,14 @@ use crate::style::TextStyle;
 use super::*;
 
 
-/// Layouts text into a box.
-///
-/// There is no complex layout involved. The text is simply laid out left-
-/// to-right using the correct font for each character.
-pub async fn layout_text(text: &str, ctx: TextContext<'_, '_>) -> Layout {
-    TextLayouter::new(text, ctx).layout().await
+/// Layouts text into boxes.
+struct TextLayouter<'a, 'p> {
+    ctx: TextContext<'a, 'p>,
+    text: &'a str,
+    actions: LayoutActions,
+    buffer: String,
+    active_font: FontIndex,
+    width: Size,
 }
 
 /// The context for text layouting.
@@ -25,14 +27,12 @@ pub struct TextContext<'a, 'p> {
     pub alignment: LayoutAlignment,
 }
 
-/// Layouts text into boxes.
-struct TextLayouter<'a, 'p> {
-    ctx: TextContext<'a, 'p>,
-    text: &'a str,
-    actions: LayoutActions,
-    buffer: String,
-    active_font: FontIndex,
-    width: Size,
+/// Layouts text into a box.
+///
+/// There is no complex layout involved. The text is simply laid out left-
+/// to-right using the correct font for each character.
+pub async fn layout_text(text: &str, ctx: TextContext<'_, '_>) -> Layout {
+    TextLayouter::new(text, ctx).layout().await
 }
 
 impl<'a, 'p> TextLayouter<'a, 'p> {
diff --git a/src/lib.rs b/src/lib.rs
index 3ebe34c2..946e16d2 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -25,22 +25,24 @@ use smallvec::smallvec;
 
 use toddle::query::{FontLoader, FontProvider, SharedFontLoader};
 
-use crate::func::Scope;
-use crate::layout::{Layouted, MultiLayout};
-use crate::syntax::{parse, ParseContext, Parsed, SyntaxModel, Position};
+use crate::layout::MultiLayout;
+use crate::layout::prelude::*;
+use crate::layout::{LayoutContext, Layouted, layout};
 use crate::style::{LayoutStyle, PageStyle, TextStyle};
+use crate::syntax::{SyntaxModel, Scope, ParseContext, Parsed, parse};
+use crate::syntax::span::Position;
 
 #[macro_use]
 mod macros;
-pub mod export;
 pub mod error;
+pub mod export;
 #[macro_use]
 pub mod func;
 pub mod layout;
 pub mod library;
-pub mod syntax;
 pub mod size;
 pub mod style;
+pub mod syntax;
 
 
 /// Transforms source code into typesetted layouts.
@@ -93,7 +95,6 @@ impl<'p> Typesetter<'p> {
 
     /// Layout a syntax tree and return the produced layout.
     pub async fn layout(&self, model: &SyntaxModel) -> Layouted<MultiLayout> {
-        use crate::layout::prelude::*;
         let margins = self.style.page.margins();
         layout(
             &model,
diff --git a/src/library/font.rs b/src/library/font.rs
index b4a6218a..07707e90 100644
--- a/src/library/font.rs
+++ b/src/library/font.rs
@@ -1,4 +1,5 @@
 use toddle::query::{FontWeight, FontStyle};
+use crate::size::FSize;
 use super::*;
 
 
@@ -79,7 +80,7 @@ function! {
     #[derive(Debug, Clone, PartialEq)]
     pub struct FontSizeFunc {
         body: Option<SyntaxModel>,
-        size: Option<ScaleSize>,
+        size: Option<FSize>,
     }
 
     parse(header, body, ctx, errors, decos) {
@@ -93,11 +94,11 @@ function! {
     layout(self, ctx, errors) {
         styled(&self.body, ctx, self.size, |t, s| {
             match s {
-                ScaleSize::Absolute(size) => {
+                FSize::Absolute(size) => {
                     t.base_font_size = size;
                     t.font_scale = 1.0;
                 }
-                ScaleSize::Scaled(scale) => t.font_scale = scale,
+                FSize::Scaled(scale) => t.font_scale = scale,
             }
         })
     }
diff --git a/src/library/layout.rs b/src/library/layout.rs
index fb8633b1..87e9c357 100644
--- a/src/library/layout.rs
+++ b/src/library/layout.rs
@@ -1,4 +1,5 @@
-use smallvec::smallvec;
+use crate::size::PSize;
+use crate::syntax::func::maps::{AxisMap, PosAxisMap};
 use super::*;
 
 
diff --git a/src/library/mod.rs b/src/library/mod.rs
index e706642f..b570c48b 100644
--- a/src/library/mod.rs
+++ b/src/library/mod.rs
@@ -1,5 +1,6 @@
 //! The standard library.
 
+use crate::syntax::Scope;
 use crate::func::prelude::*;
 
 pub_use_mod!(font);
diff --git a/src/library/page.rs b/src/library/page.rs
index 25f81bc1..7e135f59 100644
--- a/src/library/page.rs
+++ b/src/library/page.rs
@@ -1,4 +1,6 @@
+use crate::size::Size;
 use crate::style::{Paper, PaperClass};
+use crate::syntax::func::maps::{AxisMap, PaddingMap};
 use super::*;
 
 
diff --git a/src/library/spacing.rs b/src/library/spacing.rs
index 6c818292..907d5f9b 100644
--- a/src/library/spacing.rs
+++ b/src/library/spacing.rs
@@ -1,5 +1,8 @@
+use crate::size::FSize;
+use crate::layout::SpacingKind;
+
 use super::*;
-use ContentKind::*;
+use self::ContentKind::*;
 
 
 function! {
diff --git a/src/size.rs b/src/size.rs
index a5bc5d7f..9dc74dd6 100644
--- a/src/size.rs
+++ b/src/size.rs
@@ -129,7 +129,7 @@ pub type PSize = ScaleSize;
 
 /// A value in two dimensions.
 #[derive(Default, Copy, Clone, PartialEq)]
-pub struct Value2D<T: Copy> {
+pub struct Value2D<T> {
     /// The horizontal component.
     pub x: T,
     /// The vertical component.
@@ -226,13 +226,13 @@ impl<T: Copy> Value2D<T> {
     }
 }
 
-impl<T: Copy> Display for Value2D<T> where T: Display {
+impl<T> Display for Value2D<T> where T: Display {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         write!(f, "[{}, {}]", self.x, self.y)
     }
 }
 
-impl<T: Copy> Debug for Value2D<T> where T: Debug {
+impl<T> Debug for Value2D<T> where T: Debug {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         write!(f, "[{:?}, {:?}]", self.x, self.y)
     }
@@ -293,7 +293,7 @@ impl Neg for Size2D {
 
 /// A value that is stretchable in an interval from a minimal through an optimal
 /// to a maximal value.
-pub struct StretchValue<T: Copy> {
+pub struct StretchValue<T> {
     /// The minimum this value can be stretched to.
     pub min: T,
     /// The optimum for this value.
@@ -302,20 +302,20 @@ pub struct StretchValue<T: Copy> {
     pub max: T,
 }
 
-impl<T: Copy> StretchValue<T> {
+impl<T> StretchValue<T> {
     /// Create a new stretch size from minimum, optimal and maximum values.
     pub fn new(min: T, opt: T, max: T) -> StretchValue<T> {
         StretchValue { min, opt, max }
     }
 }
 
-impl<T: Copy> Display for StretchValue<T> where T: Display {
+impl<T> Display for StretchValue<T> where T: Display {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         write!(f, "({}, {}, {})", self.min, self.opt, self.max)
     }
 }
 
-impl<T: Copy> Debug for StretchValue<T> where T: Debug {
+impl<T> Debug for StretchValue<T> where T: Debug {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         write!(f, "({:?}, {:?}, {:?})", self.min, self.opt, self.max)
     }
@@ -326,7 +326,7 @@ pub type StretchSize = StretchValue<Size>;
 
 /// A value in four dimensions.
 #[derive(Default, Copy, Clone, PartialEq)]
-pub struct ValueBox<T: Copy> {
+pub struct ValueBox<T> {
     /// The left extent.
     pub left: T,
     /// The top extent.
@@ -337,7 +337,7 @@ pub struct ValueBox<T: Copy> {
     pub bottom: T,
 }
 
-impl<T: Copy> ValueBox<T> {
+impl<T: Clone> ValueBox<T> {
     /// Create a new box from four sizes.
     pub fn new(left: T, top: T, right: T, bottom: T) -> ValueBox<T> {
         ValueBox { left, top, right, bottom }
@@ -345,7 +345,12 @@ impl<T: Copy> ValueBox<T> {
 
     /// Create a box with all four fields set to the same value `s`.
     pub fn with_all(value: T) -> ValueBox<T> {
-        ValueBox { left: value, top: value, right: value, bottom: value }
+        ValueBox {
+            left: value.clone(),
+            top: value.clone(),
+            right: value.clone(),
+            bottom: value
+        }
     }
 
     /// Get a mutable reference to the value for the specified direction at the
@@ -372,25 +377,25 @@ impl<T: Copy> ValueBox<T> {
 
     /// Set the `left` and `right` values.
     pub fn set_horizontal(&mut self, value: T) {
-        self.left = value;
+        self.left = value.clone();
         self.right = value;
     }
 
     /// Set the `top` and `bottom` values.
     pub fn set_vertical(&mut self, value: T) {
-        self.top = value;
+        self.top = value.clone();
         self.bottom = value;
     }
 }
 
-impl<T: Copy> Display for ValueBox<T> where T: Display {
+impl<T> Display for ValueBox<T> where T: Display {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         write!(f, "[left: {}, top: {}, right: {}, bottom: {}]",
             self.left, self.top, self.right, self.bottom)
     }
 }
 
-impl<T: Copy> Debug for ValueBox<T> where T: Debug {
+impl<T> Debug for ValueBox<T> where T: Debug {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         write!(f, "[left: {:?}, top: {:?}, right: {:?}, bottom: {:?}]",
             self.left, self.top, self.right, self.bottom)
diff --git a/src/style.rs b/src/style.rs
index 430deaca..22ed4d2d 100644
--- a/src/style.rs
+++ b/src/style.rs
@@ -1,7 +1,6 @@
 //! Styles for text and pages.
 
 use toddle::query::{FontFallbackTree, FontVariant, FontStyle, FontWeight};
-
 use crate::size::{Size, Size2D, SizeBox, ValueBox, PSize};
 
 
diff --git a/src/syntax/expr.rs b/src/syntax/expr.rs
index fe24c655..b4c0dfaa 100644
--- a/src/syntax/expr.rs
+++ b/src/syntax/expr.rs
@@ -1,4 +1,10 @@
-use super::*;
+use std::fmt::{self, Display, Formatter};
+
+use crate::error::Errors;
+use crate::size::Size;
+use super::func::{keys::Key, values::Value};
+use super::span::{Span, Spanned};
+use super::tokens::is_identifier;
 
 
 /// An argument or return value.
@@ -91,6 +97,13 @@ pub struct Object {
     pub pairs: Vec<Pair>,
 }
 
+/// A key-value pair in an object.
+#[derive(Clone, PartialEq)]
+pub struct Pair {
+    pub key: Spanned<Ident>,
+    pub value: Spanned<Expr>,
+}
+
 impl Object {
     pub fn new() -> Object {
         Object { pairs: vec![] }
@@ -162,13 +175,6 @@ impl Object {
     }
 }
 
-/// A key-value pair in an object.
-#[derive(Clone, PartialEq)]
-pub struct Pair {
-    pub key: Spanned<Ident>,
-    pub value: Spanned<Expr>,
-}
-
 impl Display for Expr {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         use Expr::*;
diff --git a/src/syntax/func/keys.rs b/src/syntax/func/keys.rs
index dff97bde..116cd4e6 100644
--- a/src/syntax/func/keys.rs
+++ b/src/syntax/func/keys.rs
@@ -1,9 +1,10 @@
 use crate::layout::prelude::*;
+use super::values::AlignmentValue::{self, *};
 use super::*;
 
-use AxisKey::*;
-use PaddingKey::*;
-use AlignmentValue::*;
+use self::AxisKey::*;
+use self::PaddingKey::*;
+
 
 
 pub trait Key {
@@ -28,7 +29,7 @@ macro_rules! key {
             fn parse(key: Spanned<&str>) -> Option<Self::Output> {
                 match key.v {
                     $($($p)|* => Some($r)),*,
-                    other => None,
+                    _ => None,
                 }
             }
         }
diff --git a/src/syntax/func/maps.rs b/src/syntax/func/maps.rs
index 452c8ab1..8941024e 100644
--- a/src/syntax/func/maps.rs
+++ b/src/syntax/func/maps.rs
@@ -1,9 +1,11 @@
 //! Deduplicating maps and keys for argument parsing.
 
-use std::collections::HashMap;
-use std::hash::Hash;
-use crate::layout::{LayoutAxes, SpecificAxis, GenericAxis};
+use crate::error::Errors;
+use crate::layout::prelude::*;
 use crate::size::{PSize, ValueBox};
+use crate::syntax::span::Spanned;
+use super::keys::*;
+use super::values::*;
 use super::*;
 
 
@@ -179,7 +181,6 @@ impl PaddingMap {
         padding: &mut ValueBox<Option<PSize>>
     ) {
         use PaddingKey::*;
-        use SpecificAxis::*;
 
         let map = self.0.dedup(errors, |key, &val| {
             (match key {
diff --git a/src/syntax/func/mod.rs b/src/syntax/func/mod.rs
index b6691ab5..e66b4d6a 100644
--- a/src/syntax/func/mod.rs
+++ b/src/syntax/func/mod.rs
@@ -1,8 +1,10 @@
-use super::*;
+use crate::error::{Error, Errors};
+use super::expr::{Expr, Ident, Tuple, Object, Pair};
+use super::span::{Span, Spanned};
 
-pub_use_mod!(maps);
-pub_use_mod!(keys);
-pub_use_mod!(values);
+pub mod maps;
+pub mod keys;
+pub mod values;
 
 
 #[derive(Debug, Clone, PartialEq)]
@@ -17,22 +19,6 @@ pub struct FuncArgs {
     pub key: Object,
 }
 
-#[derive(Debug, Clone, PartialEq)]
-pub enum Arg {
-    Pos(Spanned<Expr>),
-    Key(Pair),
-}
-
-impl Arg {
-    /// The span or the value or combined span of key and value.
-    pub fn span(&self) -> Span {
-        match self {
-            Arg::Pos(item) => item.span,
-            Arg::Key(Pair { key, value }) => Span::merge(key.span, value.span),
-        }
-    }
-}
-
 impl FuncArgs {
     pub fn new() -> FuncArgs {
         FuncArgs {
@@ -42,10 +28,10 @@ impl FuncArgs {
     }
 
     /// Add an argument.
-    pub fn add(&mut self, arg: Arg) {
+    pub fn add(&mut self, arg: FuncArg) {
         match arg {
-            Arg::Pos(item) => self.add_pos(item),
-            Arg::Key(pair) => self.add_key_pair(pair),
+            FuncArg::Pos(item) => self.add_pos(item),
+            FuncArg::Key(pair) => self.add_key_pair(pair),
         }
     }
 
@@ -64,74 +50,27 @@ impl FuncArgs {
         self.key.add_pair(pair);
     }
 
-    pub fn into_iter(self) -> impl Iterator<Item=Arg> {
-        self.pos.items.into_iter().map(|item| Arg::Pos(item))
-            .chain(self.key.pairs.into_iter().map(|pair| Arg::Key(pair)))
+    pub fn into_iter(self) -> impl Iterator<Item=FuncArg> {
+        self.pos.items.into_iter().map(|item| FuncArg::Pos(item))
+            .chain(self.key.pairs.into_iter().map(|pair| FuncArg::Key(pair)))
     }
+}
 
-    // /// Force-extract the first positional argument.
-    // pub fn get_pos<E: ExpressionKind>(&mut self) -> ParseResult<E> {
-    //     expect(self.get_pos_opt())
-    // }
-
-    // /// Extract the first positional argument.
-    // pub fn get_pos_opt<E: ExpressionKind>(&mut self) -> ParseResult<Option<E>> {
-    //     Ok(if !self.positional.items.is_empty() {
-    //         let spanned = self.positional.items.remove(0);
-    //         Some(E::from_expr(spanned)?)
-    //     } else {
-    //         None
-    //     })
-    // }
-
-    // /// Force-extract a keyword argument.
-    // pub fn get_key<E: ExpressionKind>(&mut self, name: &str) -> ParseResult<E> {
-    //     expect(self.get_key_opt(name))
-    // }
-
-    // /// Extract a keyword argument.
-    // pub fn get_key_opt<E: ExpressionKind>(&mut self, name: &str) -> ParseResult<Option<E>> {
-    //     self.keyword.pairs.iter()
-    //         .position(|p| p.key.v.0 == name)
-    //         .map(|index| {
-    //             let value = self.keyword.pairs.swap_remove(index).value;
-    //             E::from_expr(value)
-    //         })
-    //         .transpose()
-    // }
-
-    // /// Iterator over positional arguments.
-    // pub fn iter_pos(&mut self) -> std::vec::IntoIter<Spanned<Expr>> {
-    //     let tuple = std::mem::replace(&mut self.positional, Tuple::new());
-    //     tuple.items.into_iter()
-    // }
-
-    // /// Iterator over all keyword arguments.
-    // pub fn iter_keys(&mut self) -> std::vec::IntoIter<Pair> {
-    //     let object = std::mem::replace(&mut self.keyword, Object::new());
-    //     object.pairs.into_iter()
-    // }
-
-    // /// Clear the argument lists.
-    // pub fn clear(&mut self) {
-    //     self.positional.items.clear();
-    //     self.keyword.pairs.clear();
-    // }
-
-    // /// Whether both the positional and keyword argument lists are empty.
-    // pub fn is_empty(&self) -> bool {
-    //     self.positional.items.is_empty() && self.keyword.pairs.is_empty()
-    // }
+#[derive(Debug, Clone, PartialEq)]
+pub enum FuncArg {
+    Pos(Spanned<Expr>),
+    Key(Pair),
 }
 
-// /// Extract the option expression kind from the option or return an error.
-// fn expect<E: ExpressionKind>(opt: ParseResult<Option<E>>) -> ParseResult<E> {
-//     match opt {
-//         Ok(Some(spanned)) => Ok(spanned),
-//         Ok(None) => error!("expected {}", E::NAME),
-//         Err(e) => Err(e),
-//     }
-// }
+impl FuncArg {
+    /// The span or the value or combined span of key and value.
+    pub fn span(&self) -> Span {
+        match self {
+            FuncArg::Pos(item) => item.span,
+            FuncArg::Key(Pair { key, value }) => Span::merge(key.span, value.span),
+        }
+    }
+}
 
 pub trait OptionExt: Sized {
     fn or_missing(self, errors: &mut Errors, span: Span, what: &str) -> Self;
diff --git a/src/syntax/func/values.rs b/src/syntax/func/values.rs
index b29b9726..a767aef6 100644
--- a/src/syntax/func/values.rs
+++ b/src/syntax/func/values.rs
@@ -1,12 +1,13 @@
+use std::fmt::{self, Display, Formatter};
 use std::marker::PhantomData;
 use toddle::query::{FontStyle, FontWeight};
 
 use crate::layout::prelude::*;
-use crate::size::ScaleSize;
+use crate::size::{Size, ScaleSize};
 use crate::style::Paper;
 use super::*;
 
-use AlignmentValue::*;
+use self::AlignmentValue::*;
 
 
 pub trait Value {
@@ -76,20 +77,6 @@ impl<T: Value> Value for Defaultable<T> {
     }
 }
 
-impl Value for Direction {
-    type Output = Self;
-
-    fn parse(expr: Spanned<Expr>) -> Result<Self::Output, Error> {
-        Ok(match Ident::parse(expr)?.as_str() {
-            "left-to-right" | "ltr" | "LTR" => Direction::LeftToRight,
-            "right-to-left" | "rtl" | "RTL" => Direction::RightToLeft,
-            "top-to-bottom" | "ttb" | "TTB" => Direction::TopToBottom,
-            "bottom-to-top" | "btt" | "BTT" => Direction::BottomToTop,
-            other => return Err(err!("invalid direction"))
-        })
-    }
-}
-
 impl Value for FontStyle {
     type Output = Self;
 
@@ -134,6 +121,20 @@ impl Value for Paper {
     }
 }
 
+impl Value for Direction {
+    type Output = Self;
+
+    fn parse(expr: Spanned<Expr>) -> Result<Self::Output, Error> {
+        Ok(match Ident::parse(expr)?.as_str() {
+            "left-to-right" | "ltr" | "LTR" => LeftToRight,
+            "right-to-left" | "rtl" | "RTL" => RightToLeft,
+            "top-to-bottom" | "ttb" | "TTB" => TopToBottom,
+            "bottom-to-top" | "btt" | "BTT" => BottomToTop,
+            _ => return Err(err!("invalid direction"))
+        })
+    }
+}
+
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
 pub enum AlignmentValue {
     Align(Alignment),
@@ -203,7 +204,7 @@ impl Value for AlignmentValue {
             "top"    => Top,
             "right"  => Right,
             "bottom" => Bottom,
-            other => return Err(err!("invalid alignment"))
+            _ => return Err(err!("invalid alignment"))
         })
     }
 }
diff --git a/src/syntax/mod.rs b/src/syntax/mod.rs
index 356535ae..d5afbca6 100644
--- a/src/syntax/mod.rs
+++ b/src/syntax/mod.rs
@@ -1,77 +1,25 @@
 //! Tokenization and parsing of source code.
 
 use std::any::Any;
-use std::fmt::{self, Debug, Display, Formatter};
-use std::future::Future;
-use std::pin::Pin;
+use std::fmt::Debug;
+use async_trait::async_trait;
 use serde::Serialize;
 
-use crate::error::{Error, Errors};
-use crate::func::{Commands, Command};
-use crate::layout::{Layouted, LayoutContext};
-use crate::size::Size;
+use crate::layout::{LayoutContext, Layouted, Commands, Command};
+use self::span::{Spanned, SpanVec};
 
-pub_use_mod!(expr);
-pub_use_mod!(func);
-pub_use_mod!(tokens);
-pub_use_mod!(parsing);
-pub_use_mod!(span);
+pub mod expr;
+pub mod func;
+pub mod span;
 
-/// Common syntax types.
-pub mod prelude {
-    pub use super::*;
-}
+pub_use_mod!(scope);
+pub_use_mod!(parsing);
+pub_use_mod!(tokens);
 
 
-#[async_trait::async_trait(?Send)]
+#[async_trait(?Send)]
 pub trait Model: Debug + ModelBounds {
-    async fn layout<'a>(
-        &'a self,
-        ctx: LayoutContext<'_, '_>
-    ) -> Layouted<Commands<'a>>;
-}
-
-pub type DynFuture<'a, T> = Pin<Box<dyn Future<Output=T> + 'a>>;
-
-impl dyn Model {
-    pub fn downcast<T>(&self) -> Option<&T> where T: Model + 'static {
-        self.as_any().downcast_ref::<T>()
-    }
-}
-
-impl PartialEq for dyn Model {
-    fn eq(&self, other: &dyn Model) -> bool {
-        self.bound_eq(other)
-    }
-}
-
-impl Clone for Box<dyn Model> {
-    fn clone(&self) -> Self {
-        self.bound_clone()
-    }
-}
-
-pub trait ModelBounds {
-    fn as_any(&self) -> &dyn Any;
-    fn bound_eq(&self, other: &dyn Model) -> bool;
-    fn bound_clone(&self) -> Box<dyn Model>;
-}
-
-impl<T> ModelBounds for T where T: Model + PartialEq + Clone + 'static {
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
-
-    fn bound_eq(&self, other: &dyn Model) -> bool {
-        match other.as_any().downcast_ref::<Self>() {
-            Some(other) => self == other,
-            None => false,
-        }
-    }
-
-    fn bound_clone(&self) -> Box<dyn Model> {
-        Box::new(self.clone())
-    }
+    async fn layout<'a>(&'a self, ctx: LayoutContext<'_, '_>) -> Layouted<Commands<'a>>;
 }
 
 /// A tree representation of source code.
@@ -92,7 +40,7 @@ impl SyntaxModel {
     }
 }
 
-#[async_trait::async_trait(?Send)]
+#[async_trait(?Send)]
 impl Model for SyntaxModel {
     async fn layout<'a>(&'a self, _: LayoutContext<'_, '_>) -> Layouted<Commands<'a>> {
         Layouted {
@@ -144,3 +92,44 @@ pub enum Decoration {
     InvalidFuncName,
     ArgumentKey,
 }
+
+impl dyn Model {
+    pub fn downcast<T>(&self) -> Option<&T> where T: Model + 'static {
+        self.as_any().downcast_ref::<T>()
+    }
+}
+
+impl PartialEq for dyn Model {
+    fn eq(&self, other: &dyn Model) -> bool {
+        self.bound_eq(other)
+    }
+}
+
+impl Clone for Box<dyn Model> {
+    fn clone(&self) -> Self {
+        self.bound_clone()
+    }
+}
+
+pub trait ModelBounds {
+    fn as_any(&self) -> &dyn Any;
+    fn bound_eq(&self, other: &dyn Model) -> bool;
+    fn bound_clone(&self) -> Box<dyn Model>;
+}
+
+impl<T> ModelBounds for T where T: Model + PartialEq + Clone + 'static {
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn bound_eq(&self, other: &dyn Model) -> bool {
+        match other.as_any().downcast_ref::<Self>() {
+            Some(other) => self == other,
+            None => false,
+        }
+    }
+
+    fn bound_clone(&self) -> Box<dyn Model> {
+        Box::new(self.clone())
+    }
+}
diff --git a/src/syntax/parsing.rs b/src/syntax/parsing.rs
index e726a2e0..3e3e827f 100644
--- a/src/syntax/parsing.rs
+++ b/src/syntax/parsing.rs
@@ -1,6 +1,10 @@
-use crate::func::Scope;
+use crate::error::Errors;
+use super::expr::*;
+use super::func::{FuncHeader, FuncArgs, FuncArg};
+use super::scope::Scope;
+use super::span::{Position, Span, Spanned, SpanVec, offset_spans};
+use super::tokens::{Token, Tokens, TokenizationMode};
 use super::*;
-use Token::*;
 
 
 /// The context for parsing.
@@ -37,13 +41,13 @@ pub fn parse(start: Position, src: &str, ctx: ParseContext) -> Parsed<SyntaxMode
         let span = token.span;
 
         let node = match token.v {
-            Space(newlines) => if newlines >= 2 {
+            Token::Space(newlines) => if newlines >= 2 {
                 Node::Newline
             } else {
                 Node::Space
             },
 
-            Function { header, body, terminated } => {
+            Token::Function { header, body, terminated } => {
                 let parsed: Parsed<Node> = FuncParser::new(header, body, ctx).parse();
 
                 errors.extend(offset_spans(parsed.errors, span.start));
@@ -56,15 +60,15 @@ pub fn parse(start: Position, src: &str, ctx: ParseContext) -> Parsed<SyntaxMode
                 parsed.output
             }
 
-            Star       => Node::ToggleBolder,
-            Underscore => Node::ToggleItalic,
-            Backtick   => Node::ToggleMonospace,
-            Text(text) => Node::Text(text.to_owned()),
+            Token::Star       => Node::ToggleBolder,
+            Token::Underscore => Node::ToggleItalic,
+            Token::Backtick   => Node::ToggleMonospace,
+            Token::Text(text) => Node::Text(text.to_owned()),
 
-            LineComment(_) | BlockComment(_) => continue,
+            Token::LineComment(_) | Token::BlockComment(_) => continue,
 
             other => {
-                errors.push(err!(span; "unexpected {}", name(other)));
+                errors.push(err!(span; "unexpected {}", other.name()));
                 continue;
             }
         };
@@ -140,7 +144,7 @@ impl<'s> FuncParser<'s> {
         self.skip_whitespace();
 
         let name = match self.eat() {
-            Some(Spanned { v: ExprIdent(ident), span }) => {
+            Some(Spanned { v: Token::ExprIdent(ident), span }) => {
                 Spanned { v: Ident(ident.to_string()), span }
             }
             other => {
@@ -151,7 +155,7 @@ impl<'s> FuncParser<'s> {
 
         self.skip_whitespace();
         let args = match self.eat().map(Spanned::value) {
-            Some(Colon) => self.parse_func_args(),
+            Some(Token::Colon) => self.parse_func_args(),
             Some(_) => {
                 self.expected_at("colon", name.span.end);
                 FuncArgs::new()
@@ -179,38 +183,38 @@ impl<'s> FuncParser<'s> {
     }
 
     /// Parse a positional or keyword argument.
-    fn parse_arg(&mut self) -> Option<Arg> {
+    fn parse_arg(&mut self) -> Option<FuncArg> {
         let first = self.peek()?;
         let span = first.span;
 
-        let arg = if let ExprIdent(ident) = first.v {
+        let arg = if let Token::ExprIdent(ident) = first.v {
             self.eat();
             self.skip_whitespace();
 
             let ident = Ident(ident.to_string());
-            if let Some(Equals) = self.peekv() {
+            if let Some(Token::Equals) = self.peekv() {
                 self.eat();
                 self.skip_whitespace();
 
                 self.decorations.push(Spanned::new(Decoration::ArgumentKey, span));
 
                 self.parse_expr().map(|value| {
-                    Arg::Key(Pair {
+                    FuncArg::Key(Pair {
                         key: Spanned { v: ident, span },
                         value,
                     })
                 })
             } else {
-                Some(Arg::Pos(Spanned::new(Expr::Ident(ident), span)))
+                Some(FuncArg::Pos(Spanned::new(Expr::Ident(ident), span)))
             }
         } else {
-            self.parse_expr().map(|expr| Arg::Pos(expr))
+            self.parse_expr().map(|expr| FuncArg::Pos(expr))
         };
 
         if let Some(arg) = &arg {
             self.skip_whitespace();
             match self.peekv() {
-                Some(Comma) => { self.eat(); }
+                Some(Token::Comma) => { self.eat(); }
                 Some(_) => self.expected_at("comma", arg.span().end),
                 _ => {}
             }
@@ -228,11 +232,11 @@ impl<'s> FuncParser<'s> {
         let spanned = |v| Spanned { v, span: first.span };
 
         Some(match first.v {
-            ExprIdent(i) => {
+            Token::ExprIdent(i) => {
                 self.eat();
                 spanned(Expr::Ident(Ident(i.to_string())))
             }
-            ExprStr { string, terminated } => {
+            Token::ExprStr { string, terminated } => {
                 if !terminated {
                     self.expected_at("quote", first.span.end);
                 }
@@ -240,12 +244,13 @@ impl<'s> FuncParser<'s> {
                 self.eat();
                 spanned(Expr::Str(string.to_string()))
             }
-            ExprNumber(n) => { self.eat(); spanned(Expr::Number(n)) }
-            ExprSize(s) => { self.eat(); spanned(Expr::Size(s)) }
-            ExprBool(b) => { self.eat(); spanned(Expr::Bool(b)) }
+            Token::ExprNumber(n) => { self.eat(); spanned(Expr::Number(n)) }
+            Token::ExprSize(s) => { self.eat(); spanned(Expr::Size(s)) }
+            Token::ExprBool(b) => { self.eat(); spanned(Expr::Bool(b)) }
+
+            Token::LeftParen => self.parse_tuple(),
+            Token::LeftBrace => self.parse_object(),
 
-            LeftParen => self.parse_tuple(),
-            LeftBrace => self.parse_object(),
             _ => return None,
         })
     }
@@ -255,7 +260,7 @@ impl<'s> FuncParser<'s> {
         let start = self.pos();
 
         // TODO: Do the thing.
-        self.eat_until(|t| t == RightParen, true);
+        self.eat_until(|t| t == Token::RightParen, true);
 
         let end = self.pos();
         let span = Span { start, end };
@@ -268,7 +273,7 @@ impl<'s> FuncParser<'s> {
         let start = self.pos();
 
         // TODO: Do the thing.
-        self.eat_until(|t| t == RightBrace, true);
+        self.eat_until(|t| t == Token::RightBrace, true);
 
         let end = self.pos();
         let span = Span { start, end };
@@ -278,15 +283,16 @@ impl<'s> FuncParser<'s> {
 
     /// Skip all whitespace/comment tokens.
     fn skip_whitespace(&mut self) {
-        self.eat_until(|t|
-            !matches!(t, Space(_) | LineComment(_) | BlockComment(_)), false)
+        self.eat_until(|t| !matches!(t,
+            Token::Space(_) | Token::LineComment(_) |
+            Token::BlockComment(_)), false)
     }
 
     /// Add an error about an expected `thing` which was not found, showing
     /// what was found instead.
     fn expected_found(&mut self, thing: &str, found: Spanned<Token>) {
         self.errors.push(err!(found.span;
-            "expected {}, found {}", thing, name(found.v)));
+            "expected {}, found {}", thing, found.v.name()));
     }
 
     /// Add an error about an `thing` which was expected but not found at the
@@ -348,31 +354,3 @@ impl<'s> FuncParser<'s> {
             .unwrap_or_else(|| self.tokens.pos())
     }
 }
-
-/// The name of a token in an `(un)expected <...>` error.
-fn name(token: Token) -> &'static str {
-    match token {
-        Space(_)      => "space",
-        LineComment(_) | BlockComment(_) => "comment",
-        Function { .. } => "function",
-        LeftParen     => "opening paren",
-        RightParen    => "closing paren",
-        LeftBrace     => "opening brace",
-        RightBrace    => "closing brace",
-        Colon         => "colon",
-        Comma         => "comma",
-        Equals        => "equals sign",
-        ExprIdent(_)  => "identifier",
-        ExprStr { .. }    => "string",
-        ExprNumber(_) => "number",
-        ExprSize(_)   => "size",
-        ExprBool(_)   => "boolean",
-        Star          => "star",
-        Underscore    => "underscore",
-        Backtick      => "backtick",
-        Text(_)       => "invalid identifier",
-        Invalid("]")  => "closing bracket",
-        Invalid("*/") => "end of block comment",
-        Invalid(_)    => "invalid token",
-    }
-}
diff --git a/src/func/mod.rs b/src/syntax/scope.rs
index b3721d91..2aae331d 100644
--- a/src/func/mod.rs
+++ b/src/syntax/scope.rs
@@ -1,67 +1,12 @@
-//! Dynamic typesetting functions.
-
 use std::collections::HashMap;
 use std::fmt::{self, Debug, Formatter};
 
-use self::prelude::*;
-
-#[macro_use]
-mod macros;
-
-/// Useful imports for creating your own functions.
-pub mod prelude {
-    pub use super::{Scope, Parse, Command, Commands};
-    pub use crate::error::Error;
-    pub use crate::layout::prelude::*;
-    pub use crate::syntax::prelude::*;
-    pub use crate::size::{Size, Size2D, SizeBox, ValueBox, ScaleSize, FSize, PSize};
-    pub use crate::style::{LayoutStyle, PageStyle, TextStyle};
-    pub use Command::*;
-}
-
-/// Parse a function from source code.
-pub trait Parse {
-    type Meta: Clone;
-
-    /// Parse the header and body into this function given a context.
-    fn parse(
-        header: FuncHeader,
-        body: Option<Spanned<&str>>,
-        ctx: ParseContext,
-        metadata: Self::Meta,
-    ) -> Parsed<Self> where Self: Sized;
-}
-
-/// A function which parses the source of a function into a model type which
-/// implements [`Model`].
-type Parser = dyn Fn(
-    FuncHeader,
-    Option<Spanned<&str>>,
-    ParseContext,
-) -> Parsed<Box<dyn Model>>;
-
-/// A sequence of layouting commands.
-pub type Commands<'a> = Vec<Command<'a>>;
-
-/// Layouting commands from functions to the typesetting engine.
-#[derive(Debug)]
-pub enum Command<'a> {
-    LayoutSyntaxModel(&'a SyntaxModel),
-
-    Add(Layout),
-    AddMultiple(MultiLayout),
-    AddSpacing(Size, SpacingKind, GenericAxis),
+use crate::func::ParseFunc;
+use super::func::FuncHeader;
+use super::parsing::{ParseContext, Parsed};
+use super::span::Spanned;
+use super::Model;
 
-    FinishLine,
-    FinishSpace,
-    BreakParagraph,
-    BreakPage,
-
-    SetTextStyle(TextStyle),
-    SetPageStyle(PageStyle),
-    SetAlignment(LayoutAlignment),
-    SetAxes(LayoutAxes),
-}
 
 /// A map from identifiers to function parsers.
 pub struct Scope {
@@ -73,7 +18,7 @@ impl Scope {
     /// Create a new empty scope with a fallback parser that is invoked when no
     /// match is found.
     pub fn new<F>() -> Scope
-    where F: Parse<Meta=()> + Model + 'static {
+    where F: ParseFunc<Meta=()> + Model + 'static {
         Scope {
             parsers: HashMap::new(),
             fallback: parser::<F>(()),
@@ -87,14 +32,14 @@ impl Scope {
 
     /// Associate the given name with a type that is parseable into a function.
     pub fn add<F>(&mut self, name: &str)
-    where F: Parse<Meta=()> + Model + 'static {
+    where F: ParseFunc<Meta=()> + Model + 'static {
         self.add_with_meta::<F>(name, ());
     }
 
     /// Add a parseable type with additional metadata  that is given to the
     /// parser (other than the default of `()`).
-    pub fn add_with_meta<F>(&mut self, name: &str, metadata: <F as Parse>::Meta)
-    where F: Parse + Model + 'static {
+    pub fn add_with_meta<F>(&mut self, name: &str, metadata: <F as ParseFunc>::Meta)
+    where F: ParseFunc + Model + 'static {
         self.parsers.insert(
             name.to_owned(),
             parser::<F>(metadata),
@@ -121,7 +66,16 @@ impl Debug for Scope {
     }
 }
 
-fn parser<F>(metadata: <F as Parse>::Meta) -> Box<Parser> where F: Parse + Model + 'static {
+/// A function which parses the source of a function into a model type which
+/// implements [`Model`].
+type Parser = dyn Fn(
+    FuncHeader,
+    Option<Spanned<&str>>,
+    ParseContext,
+) -> Parsed<Box<dyn Model>>;
+
+fn parser<F>(metadata: <F as ParseFunc>::Meta) -> Box<Parser>
+where F: ParseFunc + Model + 'static {
     Box::new(move |h, b, c| {
         F::parse(h, b, c, metadata.clone())
             .map(|model| Box::new(model) as Box<dyn Model>)
diff --git a/src/syntax/span.rs b/src/syntax/span.rs
index e049861f..f5bd4caf 100644
--- a/src/syntax/span.rs
+++ b/src/syntax/span.rs
@@ -5,45 +5,56 @@ use std::ops::{Add, Sub};
 use serde::Serialize;
 
 
-/// Annotates a value with the part of the source code it corresponds to.
-#[derive(Copy, Clone, Eq, PartialEq, Hash, Serialize)]
-pub struct Spanned<T> {
-    pub v: T,
-    pub span: Span,
+/// A line-column position in source code.
+#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Serialize)]
+pub struct Position {
+    /// The 0-indexed line (inclusive).
+    pub line: usize,
+    /// The 0-indexed column (inclusive).
+    pub column: usize,
 }
 
-impl<T> Spanned<T> {
-    pub fn new(v: T, span: Span) -> Spanned<T> {
-        Spanned { v, span }
-    }
+impl Position {
+    pub const ZERO: Position = Position { line: 0, column: 0 };
 
-    pub fn value(self) -> T {
-        self.v
+    pub fn new(line: usize, column: usize) -> Position {
+        Position { line, column }
     }
+}
 
-    pub fn map<V, F>(self, f: F) -> Spanned<V> where F: FnOnce(T) -> V {
-        Spanned { v: f(self.v), span: self.span }
-    }
+impl Add for Position {
+    type Output = Position;
 
-    pub fn map_span<F>(mut self, f: F) -> Spanned<T> where F: FnOnce(Span) -> Span {
-        self.span = f(self.span);
-        self
+    fn add(self, rhs: Position) -> Position {
+        if rhs.line == 0 {
+            Position {
+                line: self.line,
+                column: self.column + rhs.column
+            }
+        } else {
+            Position {
+                line: self.line + rhs.line,
+                column: rhs.column,
+            }
+        }
     }
 }
 
-impl<T> Display for Spanned<T> where T: std::fmt::Display {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "({}, {}, ", self.span.start, self.span.end)?;
-        self.v.fmt(f)?;
-        write!(f, ")")
-    }
-}
+impl Sub for Position {
+    type Output = Position;
 
-impl<T> Debug for Spanned<T> where T: std::fmt::Debug {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "({}, {}, ", self.span.start, self.span.end)?;
-        self.v.fmt(f)?;
-        write!(f, ")")
+    fn sub(self, rhs: Position) -> Position {
+        if self.line == rhs.line {
+            Position {
+                line: 0,
+                column: self.column - rhs.column
+            }
+        } else {
+            Position {
+                line: self.line - rhs.line,
+                column: self.column,
+            }
+        }
     }
 }
 
@@ -84,65 +95,37 @@ impl Span {
     }
 }
 
-impl Display for Span {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "({}, {})", self.start, self.end)
-    }
-}
-
-debug_display!(Span);
-
-/// A line-column position in source code.
-#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Serialize)]
-pub struct Position {
-    /// The 0-indexed line (inclusive).
-    pub line: usize,
-    /// The 0-indexed column (inclusive).
-    pub column: usize,
+/// Annotates a value with the part of the source code it corresponds to.
+#[derive(Copy, Clone, Eq, PartialEq, Hash, Serialize)]
+pub struct Spanned<T> {
+    pub v: T,
+    pub span: Span,
 }
 
-impl Position {
-    pub const ZERO: Position = Position { line: 0, column: 0 };
+impl<T> Spanned<T> {
+    pub fn new(v: T, span: Span) -> Spanned<T> {
+        Spanned { v, span }
+    }
 
-    pub fn new(line: usize, column: usize) -> Position {
-        Position { line, column }
+    pub fn value(self) -> T {
+        self.v
     }
-}
 
-impl Add for Position {
-    type Output = Position;
+    pub fn map<V, F>(self, f: F) -> Spanned<V> where F: FnOnce(T) -> V {
+        Spanned { v: f(self.v), span: self.span }
+    }
 
-    fn add(self, rhs: Position) -> Position {
-        if rhs.line == 0 {
-            Position {
-                line: self.line,
-                column: self.column + rhs.column
-            }
-        } else {
-            Position {
-                line: self.line + rhs.line,
-                column: rhs.column,
-            }
-        }
+    pub fn map_span<F>(mut self, f: F) -> Spanned<T> where F: FnOnce(Span) -> Span {
+        self.span = f(self.span);
+        self
     }
 }
 
-impl Sub for Position {
-    type Output = Position;
+/// A vector of spanned things.
+pub type SpanVec<T> = Vec<Spanned<T>>;
 
-    fn sub(self, rhs: Position) -> Position {
-        if self.line == rhs.line {
-            Position {
-                line: 0,
-                column: self.column - rhs.column
-            }
-        } else {
-            Position {
-                line: self.line - rhs.line,
-                column: self.column,
-            }
-        }
-    }
+pub fn offset_spans<T>(vec: SpanVec<T>, start: Position) -> impl Iterator<Item=Spanned<T>> {
+    vec.into_iter().map(move |s| s.map_span(|span| span.offset(start)))
 }
 
 impl Display for Position {
@@ -151,11 +134,27 @@ impl Display for Position {
     }
 }
 
-debug_display!(Position);
+impl Display for Span {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "({}, {})", self.start, self.end)
+    }
+}
 
-/// A vector of spanned things.
-pub type SpanVec<T> = Vec<Spanned<T>>;
+impl<T> Display for Spanned<T> where T: std::fmt::Display {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "({}, {}, ", self.span.start, self.span.end)?;
+        self.v.fmt(f)?;
+        write!(f, ")")
+    }
+}
 
-pub fn offset_spans<T>(vec: SpanVec<T>, start: Position) -> impl Iterator<Item=Spanned<T>> {
-    vec.into_iter().map(move |s| s.map_span(|span| span.offset(start)))
+impl<T> Debug for Spanned<T> where T: std::fmt::Debug {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "({}, {}, ", self.span.start, self.span.end)?;
+        self.v.fmt(f)?;
+        write!(f, ")")
+    }
 }
+
+debug_display!(Position);
+debug_display!(Span);
diff --git a/src/syntax/tokens.rs b/src/syntax/tokens.rs
index d0adbf60..0a8e2f17 100644
--- a/src/syntax/tokens.rs
+++ b/src/syntax/tokens.rs
@@ -2,9 +2,11 @@ use std::iter::Peekable;
 use std::str::Chars;
 use unicode_xid::UnicodeXID;
 
-use super::*;
-use Token::*;
-use TokenizationMode::*;
+use crate::size::Size;
+use super::span::{Position, Span, Spanned};
+
+use self::Token::*;
+use self::TokenizationMode::*;
 
 
 /// A minimal semantic entity of source code.
@@ -68,6 +70,37 @@ pub enum Token<'s> {
     Invalid(&'s str),
 }
 
+impl<'s> Token<'s> {
+    /// The natural-language name for this token for use in error messages.
+    pub fn name(self) -> &'static str {
+        match self {
+            Space(_)        => "space",
+            LineComment(_)  => "line comment",
+            BlockComment(_) => "block comment",
+            Function { .. } => "function",
+            LeftParen       => "opening paren",
+            RightParen      => "closing paren",
+            LeftBrace       => "opening brace",
+            RightBrace      => "closing brace",
+            Colon           => "colon",
+            Comma           => "comma",
+            Equals          => "equals sign",
+            ExprIdent(_)    => "identifier",
+            ExprStr { .. }  => "string",
+            ExprNumber(_)   => "number",
+            ExprSize(_)     => "size",
+            ExprBool(_)     => "boolean",
+            Star            => "star",
+            Underscore      => "underscore",
+            Backtick        => "backtick",
+            Text(_)         => "invalid identifier",
+            Invalid("]")    => "closing bracket",
+            Invalid("*/")   => "end of block comment",
+            Invalid(_)      => "invalid token",
+        }
+    }
+}
+
 /// An iterator over the tokens of a string of source code.
 pub struct Tokens<'s> {
     src: &'s str,