Skip to content

coroc: support for range loops over strings #138

Open
Open
coroc: support for range loops over strings#138
Labels
enhancementNew feature or request

Description

@chriso
chriso
opened on Dec 16, 2023

The desugaring pass should be updated to desugar for range loops over strings:

var s string
for range string { ... }
for index := range string { ... }
for index, rune := range string { ... }

At first glance it should simply be a matter of adding *types.Basic (with .Kind() == types.String) to the case where we handle *types.Array and *types.Slice here, however range loops are a bit different when strings are involved. When indexing a string you get back a byte. When using a for range loop with a string you get a rune along with an index representing its offset in the string. More info in https://go.dev/blog/strings.

The desugaring pass should use utf.DecodeRuneInString to parse runes from strings iteratively.

Activity

  1. chriso commented on Dec 16, 2023

    @chriso
    chriso
    on Dec 16, 2023
    ContributorAuthor

    Test case:

    diff --git i/compiler/coroutine_test.go w/compiler/coroutine_test.go
index 85fa53b..ca9be36 100644
--- i/compiler/coroutine_test.go
+++ w/compiler/coroutine_test.go
@@ -243,6 +243,16 @@ func TestCoroutineYield(t *testing.T) {
                        coro:   func() { IdentityGenericStructClosureInt(11) },
                        yields: []int{11, 100, 23, 12, 101, 45},
                },
+
+               {
+                       name: "range over string",
+                       coro: func() { RangeOverString("foo") },
+                       yields: []int{
+                               0, 0, 0,
+                               0, 1, 2,
+                               0, 'f', 1, 'o', 2, 'o',
+                       },
+               },
        }
 
        // This emulates the installation of function type information by the
diff --git i/compiler/testdata/coroutine.go w/compiler/testdata/coroutine.go
index 36b42ff..1a11938 100644
--- i/compiler/testdata/coroutine.go
+++ w/compiler/testdata/coroutine.go
@@ -636,3 +636,16 @@ func IdentityGenericStructClosureInt(n int) {
        fn(23)
        fn(45)
 }
+
+func RangeOverString(s string) {
+       for range s {
+               coroutine.Yield[int, any](0)
+       }
+       for i := range s {
+               coroutine.Yield[int, any](i)
+       }
+       for i, c := range s {
+               coroutine.Yield[int, any](i)
+               coroutine.Yield[int, any](int(c))
+       }
+}
  2. chriso
    added
    enhancementNew feature or request
    on Dec 16, 2023
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Metadata

Metadata

Assignees

No one assigned

    Labels

    enhancementNew feature or request

    Type

    No type

    Projects

    No projects

      Milestone

      No milestone

      Relationships

      None yet

      Development

      No branches or pull requests

      Issue actions