Counters

2 files changed, 25 insertions, 1 deletions

diff --git a/src/eval/library.rs b/src/eval/library.rs
index 1240d9bb..45c23d17 100644
--- a/src/eval/library.rs
+++ b/src/eval/library.rs
@@ -6,11 +6,12 @@ use comemo::Tracked;
 use ecow::EcoString;
 use once_cell::sync::OnceCell;
 
-use super::Module;
+use super::{Args, Dynamic, Module, Value};
 use crate::diag::SourceResult;
 use crate::doc::Document;
 use crate::geom::{Abs, Dir};
 use crate::model::{Content, Introspector, Label, NodeId, StyleChain, StyleMap, Vt};
+use crate::syntax::Span;
 use crate::util::hash128;
 use crate::World;
 
@@ -89,6 +90,14 @@ pub struct LangItems {
     pub math_accent: fn(base: Content, accent: char) -> Content,
     /// A fraction in a formula: `x/2`.
     pub math_frac: fn(num: Content, denom: Content) -> Content,
+    /// Dispatch a method on a counter. This is hacky and should be superseded
+    /// by more dynamic method dispatch.
+    pub counter_method: fn(
+        dynamic: &Dynamic,
+        method: &str,
+        args: Args,
+        span: Span,
+    ) -> SourceResult<Value>,
 }
 
 impl Debug for LangItems {
diff --git a/src/eval/methods.rs b/src/eval/methods.rs
index 197a2f65..a449ac16 100644
--- a/src/eval/methods.rs
+++ b/src/eval/methods.rs
@@ -134,6 +134,14 @@ pub fn call(
             _ => return missing(),
         },
 
+        Value::Dyn(dynamic) => {
+            if dynamic.type_name() == "counter" {
+                return (vm.items.counter_method)(&dynamic, method, args, span);
+            }
+
+            return missing();
+        }
+
         _ => return missing(),
     };
 
@@ -281,6 +289,13 @@ pub fn methods_on(type_name: &str) -> &[(&'static str, bool)] {
         ],
         "function" => &[("where", true), ("with", true)],
         "arguments" => &[("named", false), ("pos", false)],
+        "counter" => &[
+            ("get", true),
+            ("final", true),
+            ("both", true),
+            ("step", true),
+            ("update", true),
+        ],
         _ => &[],
     }
 }