Add sum and product to arrays (#966)

2 files changed, 37 insertions, 0 deletions

diff --git a/src/eval/array.rs b/src/eval/array.rs
index b04fdab8..1166ce94 100644
--- a/src/eval/array.rs
+++ b/src/eval/array.rs
@@ -24,6 +24,7 @@ macro_rules! __array {
 
 #[doc(inline)]
 pub use crate::__array as array;
+use crate::eval::ops::{add, mul};
 #[doc(hidden)]
 pub use ecow::eco_vec;
 
@@ -199,6 +200,40 @@ impl Array {
         Ok(acc)
     }
 
+    /// Calculates the sum of the array's items
+    pub fn sum(&self, default: Option<Value>, span: Span) -> SourceResult<Value> {
+        let mut acc = self
+            .first()
+            .map(|x| x.clone())
+            .or_else(|_| {
+                default.ok_or_else(|| {
+                    eco_format!("cannot calculate sum of empty array with no default")
+                })
+            })
+            .at(span)?;
+        for i in self.iter().skip(1) {
+            acc = add(acc, i.clone()).at(span)?;
+        }
+        Ok(acc)
+    }
+
+    /// Calculates the product of the array's items
+    pub fn product(&self, default: Option<Value>, span: Span) -> SourceResult<Value> {
+        let mut acc = self
+            .first()
+            .map(|x| x.clone())
+            .or_else(|_| {
+                default.ok_or_else(|| {
+                    eco_format!("cannot calculate product of empty array with no default")
+                })
+            })
+            .at(span)?;
+        for i in self.iter().skip(1) {
+            acc = mul(acc, i.clone()).at(span)?;
+        }
+        Ok(acc)
+    }
+
     /// Whether any item matches.
     pub fn any(&self, vm: &mut Vm, func: Func) -> SourceResult<bool> {
         for item in self.iter() {
diff --git a/src/eval/methods.rs b/src/eval/methods.rs
index 56d1c7b7..29b729cb 100644
--- a/src/eval/methods.rs
+++ b/src/eval/methods.rs
@@ -105,6 +105,8 @@ pub fn call(
             "fold" => {
                 array.fold(vm, args.expect("initial value")?, args.expect("function")?)?
             }
+            "sum" => array.sum(args.named("default")?, span)?,
+            "product" => array.product(args.named("default")?, span)?,
             "any" => Value::Bool(array.any(vm, args.expect("function")?)?),
             "all" => Value::Bool(array.all(vm, args.expect("function")?)?),
             "flatten" => Value::Array(array.flatten()),