Add List.forEach! builtin

crates/compiler/builtins/roc/List.roc

@@ -70,6 +70,7 @@ module [
     countIf,
     chunksOf,
     concatUtf8,
+    forEach!,
 ]
 
 import Bool exposing [Bool, Eq]
@@ -1383,3 +1384,20 @@ concatUtf8 : List U8, Str -> List U8
 
 expect (List.concatUtf8 [1, 2, 3, 4] "🐦") == [1, 2, 3, 4, 240, 159, 144, 166]
 
+
+## Run an effectful function for each element on the list.
+##
+## ```roc
+## List.forEach! ["Alice", "Bob", "Charlie"] \name ->
+##     createAccount! name
+##     log! "Account created"
+## ```
+forEach! : List a, (a => {}) => {}
+forEach! = \l, f! ->
+    when l is
+        [] ->
+            {}
+
+        [x, .. as xs] ->
+            f! x
+            forEach! xs f!

crates/compiler/module/src/symbol.rs

@@ -1509,7 +1509,7 @@ define_builtins! {
         87 LIST_CLONE: "clone"
         88 LIST_LEN_USIZE: "lenUsize"
         89 LIST_CONCAT_UTF8: "concatUtf8"
-        90 LIST_WALK_FX: "walk!"
+        90 LIST_FOR_EACH_FX: "forEach!"
     }
     7 RESULT: "Result" => {
         0 RESULT_RESULT: "Result" exposed_type=true // the Result.Result type alias

examples/cli/effects.roc

@@ -5,7 +5,7 @@ import pf.Effect
 main! : {} => {}
 main! = \{} ->
     ["Welcome!", "What's your name?"]
-    |> forEach! Effect.putLine!
+    |> List.forEach! Effect.putLine!
 
     line = Effect.getLine! {}
 
@@ -17,11 +17,3 @@ main! = \{} ->
 
     Effect.putLine! "You entered: $(line)"
     Effect.putLine! "It is known"
-
-forEach! : List a, (a => {}) => {}
-forEach! = \l, f! ->
-    when l is
-        [] -> {}
-        [x, .. as xs] ->
-            f! x
-            forEach! xs f!