Merge pull request #1657 from DanielXMoore/more-for

`for concat` reduction for concatenating arrays, `for first` reduction for finding elements

civet.dev/reference.md

@@ -1982,6 +1982,19 @@ numEven := for count item of array
 numKeys := for count key in object
 </Playground>
 
+`for first` returns the first body value.
+If there is no body, it uses the item being looped over.
+Combined with a `when` condition, this can act like
+[`Array.prototype.find`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find).
+
+<Playground>
+firstEven :=
+  for first item of array when item % 2 === 0
+firstEvenSquare :=
+  for first item of array when item % 2 === 0
+    item * item
+</Playground>
+
 `for sum` adds up the body values with `+`, starting from `0`.
 If there is no body, it adds the item being looped over.
 
@@ -2013,10 +2026,19 @@ It's like `for sum` but starting from `""` instead of `0`.
 
 <Playground>
 all := for join item of array
-  `[${item.type}] ${item.title}`
+  `[${item.type}] ${item.title}\n`
+</Playground>
+
+`for concat` concatenates the body values as arrays,
+using the [concat operator `++`](#concat-operator).
+If there is no body, it uses the item being looped over.
+
+<Playground>
+function flat1<T>(arrays: T[][]): T[]
+  for concat array of arrays
 </Playground>
 
-Implicit bodies in `for sum/product/min/max/join` reductions
+Implicit bodies in `for sum/product/min/max/join/concat` reductions
 can use a single destructuring:
 
 <Playground>

source/parser.hera

@@ -4774,7 +4774,7 @@ ForStatementControlWithReduction
     return { ...control, reduction }
 
 ForReduction
-  ( "some" / "every" / "count" / "sum" / "product" / "min" / "max" / "join" ):subtype NonIdContinue __:ws ->
+  ( "some" / "every" / "count" / "first" / "sum" / "product" / "min" / "max" / "join" / "concat" ):subtype NonIdContinue __:ws ->
     return {
       type: "ForReduction",
       subtype,

source/parser/function.civet

@@ -744,10 +744,12 @@ function iterationDeclaration(statement: IterationStatement | ForStatement)
       switch reduction.subtype
         when "some" then "false"
         when "every" then "true"
+        when "first" then "undefined"
         when "min" then "Infinity"
         when "max" then "-Infinity"
         when "product" then "1"
         when "join" then '""'
+        when "concat" then "[]"
         else "0"
   else if statement.object
     declaration.children.push "={}"
@@ -775,7 +777,11 @@ function iterationDeclaration(statement: IterationStatement | ForStatement)
               resultsRef, " = false; break}" ]
           when "count"
             [ "if (", node, ") ++", resultsRef ]
+          when "first"
+            [ resultsRef, " = ", node, "; break" ]
           when "sum", "join" then [ resultsRef, " += ", node ]
+          when "concat"
+            [ getHelperRef("concatAssign"), "(", resultsRef, ", ", node, ")" ]
           when "product" then [ resultsRef, " *= ", node ]
           when "min" then [ resultsRef, " = Math.min(", resultsRef, ", ", node, ")" ]
           when "max" then [ resultsRef, " = Math.max(", resultsRef, ", ", node, ")" ]

source/parser/types.civet

@@ -440,7 +440,7 @@ export type ForDeclaration
 
 export type ForReduction
   type: "ForReduction"
-  subtype: "some" | "every" | "count" | "sum" | "product" | "min" | "max" | "join"
+  subtype: "some" | "every" | "count" | "find" | "sum" | "product" | "min" | "max" | "first" | "concat"
 
 export type SwitchStatement
   type: "SwitchStatement"

test/for.civet

@@ -1461,6 +1461,37 @@ describe "for", ->
       const h =(()=>{let results7="";for (const x of y) { results7 +=  x }return results7})()
     """
 
+    testCase """
+      for concat
+      ---
+      flat := for concat x of y
+      numbers := for concat x of y
+        [x, x+1]
+      ---
+      var concatAssign: <B, A extends {push: (this: A, b: B) => void} | (B extends unknown[] ? {push: (this: A, ...b: B) => void} : never)>(lhs: A, rhs: B) => A = (lhs, rhs) => (((rhs as any)?.[Symbol.isConcatSpreadable] ?? Array.isArray(rhs)) ? (lhs as any).push.apply(lhs, rhs as any) : (lhs as any).push(rhs), lhs);
+      let results=[];for (const x of y) {concatAssign(results, x)};const flat =results
+      let results1=[];for (const x of y) {
+        concatAssign(results1, [x, x+1])
+      };const numbers =results1
+    """
+
+    testCase """
+      for first
+      ---
+      first := for first x of y
+      positive := for first x of y when x > 0
+      complex := for first x of y
+        continue unless x > 0
+        x * x
+      ---
+      let results=undefined;for (const x of y) {results = x; break};const first =results
+      let results1=undefined;for (const x of y) {if (!(x > 0)) continue;results1 = x; break};const positive =results1
+      let results2=undefined;for (const x of y) {
+        if (!(x > 0)) { continue }
+        results2 = x * x; break
+      };const complex =results2
+    """
+
     testCase """
       implicit body array destructuring
       ---