Min and max functions

src/library/math.rs

@@ -0,0 +1,60 @@
+use std::cmp::Ordering;
+
+use super::*;
+
+/// `min`: The minimum of two values.
+///
+/// # Positional parameters
+/// - Values: variadic, must be comparable.
+///
+/// # Return value
+/// The minimum of the sequence of values. For equal elements, the first one is
+/// returned.
+pub fn min(ctx: &mut EvalContext, args: &mut FuncArgs) -> Value {
+    minmax(ctx, args, Ordering::Less)
+}
+
+/// `max`: The maximum of two values.
+///
+/// # Positional parameters
+/// - Values: variadic, must be comparable.
+///
+/// # Return value
+/// The maximum of the sequence of values. For equal elements, the first one is
+/// returned.
+pub fn max(ctx: &mut EvalContext, args: &mut FuncArgs) -> Value {
+    minmax(ctx, args, Ordering::Greater)
+}
+
+/// Find the minimum or maximum of a sequence of values.
+fn minmax(ctx: &mut EvalContext, args: &mut FuncArgs, which: Ordering) -> Value {
+    let mut values = args.filter::<Value>(ctx);
+    let mut extremum = None;
+
+    for value in &mut values {
+        if let Some(prev) = &extremum {
+            match value.cmp(&prev) {
+                Some(ord) if ord == which => extremum = Some(value),
+                Some(_) => {}
+                None => {
+                    drop(values);
+                    ctx.diag(error!(
+                        args.span,
+                        "cannot compare {} with {}",
+                        prev.type_name(),
+                        value.type_name(),
+                    ));
+                    return Value::Error;
+                }
+            }
+        } else {
+            extremum = Some(value);
+        }
+    }
+
+    drop(values);
+    extremum.unwrap_or_else(|| {
+        args.require::<Value>(ctx, "value");
+        Value::Error
+    })
+}

src/library/mod.rs

@@ -9,6 +9,7 @@ mod font;
 mod image;
 mod lang;
 mod markup;
+mod math;
 mod pad;
 mod page;
 mod par;
@@ -21,6 +22,7 @@ pub use basic::*;
 pub use font::*;
 pub use lang::*;
 pub use markup::*;
+pub use math::*;
 pub use pad::*;
 pub use page::*;
 pub use par::*;
@@ -69,6 +71,8 @@ pub fn _new() -> Scope {
     func!("h", h);
     func!("image", image);
     func!("lang", lang);
+    func!("max", max);
+    func!("min", min);
     func!("pad", pad);
     func!("page", page);
     func!("pagebreak", pagebreak);

tests/typ/library/math.typ

@@ -0,0 +1,15 @@
+// Test math functions.
+// Ref: false
+
+---
+// Test `min` and `max` functions.
+#test(min(2, -4), -4)
+#test(min(3.5, 1e2, -0.1, 3), -0.1)
+#test(max(-3, 11), 11)
+#test(min("hi"), "hi")
+
+// Error: 6 missing argument: value
+#min()
+
+// Error: 11-18 cannot compare integer with string
+#test(min(1, "hi"), error)