Implement rev() method on string (#2013)

crates/typst/src/eval/methods.rs

@@ -82,6 +82,7 @@ pub fn call(
                 let count = args.named("count")?;
                 string.replace(vm, pattern, with, count)?.into_value()
             }
+            "rev" => string.rev().into_value(),
             "trim" => {
                 let pattern = args.eat()?;
                 let at = args.named("at")?;

crates/typst/src/eval/str.rs

@@ -324,6 +324,11 @@ impl Str {
         Ok(Self(self.0.repeat(n)))
     }
 
+    /// Reverse the string.
+    pub fn rev(&self) -> Self {
+        self.as_str().graphemes(true).rev().collect::<String>().into()
+    }
+
     /// Resolve an index or throw an out of bounds error.
     fn locate(&self, index: i64) -> StrResult<usize> {
         self.locate_opt(index)?

docs/reference/types.md

@@ -689,6 +689,11 @@ string and returns the resulting string.
   If given, only the first `count` matches of the pattern are placed.
 - returns: string
 
+### rev()
+Reverses the grapheme clusters and returns the resulting string.
+
+- returns: string
+
 ### trim()
 Removes matches of a pattern from one or both sides of the string, once or
 repeatedly and returns the resulting string.

tests/typ/compiler/string.typ

@@ -210,6 +210,15 @@
 #test("a123c".split(regex("\d")), ("a", "", "", "c"))
 #test("a123c".split(regex("\d+")), ("a", "c"))
 
+---
+// Test the `rev` method.
+#test("abc".rev(), "cba")
+#test("ax̂e".rev(), "ex̂a")
+
+---
+// Error: 12-15 unknown variable: arg
+#"abc".rev(arg)
+
 ---
 // Error: 2-2:1 unclosed string
 #"hello\"