Len function for strings, arrays and dictionaries

src/library/basic.rs

@@ -31,6 +31,20 @@ pub fn repr(ctx: &mut EvalContext, args: &mut FuncArgs) -> Value {
     }
 }
 
+/// `len`: The length of a string, an array or a dictionary.
+pub fn len(ctx: &mut EvalContext, args: &mut FuncArgs) -> Value {
+    match args.eat_expect::<Spanned<Value>>(ctx, "collection") {
+        Some(Spanned { v: Value::Str(v), .. }) => Value::Int(v.len() as i64),
+        Some(Spanned { v: Value::Array(v), .. }) => Value::Int(v.len() as i64),
+        Some(Spanned { v: Value::Dict(v), .. }) => Value::Int(v.len() as i64),
+        Some(other) if other.v != Value::Error => {
+            ctx.diag(error!(other.span, "expected string, array or dictionary"));
+            Value::Error
+        }
+        _ => Value::Error,
+    }
+}
+
 /// `rgb`: Create an RGB(A) color.
 ///
 /// # Positional parameters

src/library/mod.rs

@@ -56,6 +56,7 @@ pub fn new() -> Scope {
     std.def_func("h", h);
     std.def_func("image", image);
     std.def_func("lang", lang);
+    std.def_func("len", len);
     std.def_func("max", max);
     std.def_func("min", min);
     std.def_func("overline", overline);

tests/typ/utility/basics.typ

@@ -0,0 +1,16 @@
+// Test basic functions.
+// Ref: false
+
+---
+// Test the `len` function.
+
+#test(len(()), 0)
+#test(len(("A", "B", "C")), 3)
+#test(len("Hello World!"), 12)
+#test(len((a: 1, b: 2)), 2)
+
+// Error: 6 missing argument: collection
+#len()
+
+// Error: 6-10 expected string, array or dictionary
+#len(12pt)

tests/typ/utility/math.typ

@@ -1,4 +1,4 @@
-// Test basic calculation functions.
+// Test math functions.
 // Ref: false
 
 ---