Find optionally takes function instead of value

src/eval/array.rs

@@ -3,9 +3,9 @@ use std::fmt::{self, Debug, Formatter, Write};
 use std::ops::{Add, AddAssign};
 use std::sync::Arc;
 
-use super::{ops, Args, Func, Machine, Value};
+use super::{ops, Args, Cast, Func, Machine, Value};
 use crate::diag::{At, StrResult, TypResult};
-use crate::syntax::Spanned;
+use crate::syntax::{Span, Spanned};
 use crate::util::ArcExt;
 
 /// Create a new [`Array`] from values.
@@ -120,10 +120,19 @@ impl Array {
 
     /// Transform each item in the array with a function.
     pub fn map(&self, vm: &mut Machine, f: Spanned<Func>) -> TypResult<Self> {
+        let enumerate = f.v.argc() == Some(2);
         Ok(self
             .iter()
             .cloned()
-            .map(|item| f.v.call(vm, Args::new(f.span, [item])))
+            .enumerate()
+            .map(|(i, item)| {
+                let mut args = Args::new(f.span, []);
+                if enumerate {
+                    args.push(f.span, Value::Int(i as i64));
+                }
+                args.push(f.span, item);
+                f.v.call(vm, args)
+            })
             .collect::<TypResult<_>>()?)
     }
 
@@ -157,8 +166,14 @@ impl Array {
     }
 
     /// Return the index of the element if it is part of the array.
-    pub fn find(&self, value: Value) -> Option<i64> {
-        self.0.iter().position(|x| *x == value).map(|i| i as i64)
+    pub fn find(&self, vm: &mut Machine, target: Target) -> TypResult<Option<i64>> {
+        for (i, item) in self.iter().enumerate() {
+            if target.matches(vm, item)? {
+                return Ok(Some(i as i64));
+            }
+        }
+
+        Ok(None)
     }
 
     /// Join all values in the array, optionally with separator and last
@@ -304,3 +319,37 @@ impl<'a> IntoIterator for &'a Array {
         self.iter()
     }
 }
+
+/// Something that can be found.
+pub enum Target {
+    /// A bare value.
+    Value(Value),
+    /// A function that returns a boolean.
+    Func(Func, Span),
+}
+
+impl Target {
+    /// Whether the value is the search target.
+    pub fn matches(&self, vm: &mut Machine, other: &Value) -> TypResult<bool> {
+        match self {
+            Self::Value(value) => Ok(value == other),
+            Self::Func(f, span) => f
+                .call(vm, Args::new(*span, [other.clone()]))?
+                .cast::<bool>()
+                .at(*span),
+        }
+    }
+}
+
+impl Cast<Spanned<Value>> for Target {
+    fn is(_: &Spanned<Value>) -> bool {
+        true
+    }
+
+    fn cast(value: Spanned<Value>) -> StrResult<Self> {
+        Ok(match value.v {
+            Value::Func(v) => Self::Func(v, value.span),
+            v => Self::Value(v),
+        })
+    }
+}

src/eval/methods.rs

@@ -38,7 +38,9 @@ pub fn call(
             "map" => Value::Array(array.map(vm, args.expect("function")?)?),
             "filter" => Value::Array(array.filter(vm, args.expect("function")?)?),
             "flatten" => Value::Array(array.flatten()),
-            "find" => array.find(args.expect("value")?).map_or(Value::None, Value::Int),
+            "find" => array
+                .find(vm, args.expect("value or function")?)?
+                .map_or(Value::None, Value::Int),
             "join" => {
                 let sep = args.eat()?;
                 let last = args.named("last")?;

src/eval/value.rs

@@ -713,9 +713,9 @@ castable! {
 castable! {
     Pattern,
     Expected: "function, string or regular expression",
-    Value::Func(func) => Pattern::Node(func.node()?),
-    Value::Str(text) => Pattern::text(&text),
-    @regex: Regex => Pattern::Regex(regex.clone()),
+    Value::Func(func) => Self::Node(func.node()?),
+    Value::Str(text) => Self::text(&text),
+    @regex: Regex => Self::Regex(regex.clone()),
 }
 
 #[cfg(test)]

tests/typ/utility/collection.typ

@@ -32,6 +32,7 @@
 // Test the `find` method.
 #test(("Hi", "❤️", "Love").find("❤️"), 1)
 #test(("Bye", "💘", "Apart").find("❤️"), none)
+#test(("A", "B", "CDEF", "G").find(v => v.len() > 2), 2)
 
 ---
 // Test the `slice` method.