Merge pull request #1148 from DanielXMoore/infinite-for

Infinite range [x..]

source/generate.civet

@@ -9,6 +9,12 @@ type Options =
   js?: boolean
   errors?: unknown[]
 
+function stringify(node: ???): string
+  try
+    return JSON.stringify node
+  catch e
+    return `${node}`
+
 function gen(node: any, options: Options): string
   if node is null or node is undefined
     return ""
@@ -45,15 +51,15 @@ function gen(node: any, options: Options): string
     if !node.children
       switch node.type
         when "Ref"
-          throw new Error(`Unpopulated ref ${JSON.stringify(node)}`)
+          throw new Error(`Unpopulated ref ${stringify node}`)
 
       debugger
-      throw new Error(`Unknown node ${JSON.stringify(node)}`)
+      throw new Error(`Unknown node ${stringify node}`)
 
     return gen node.children, options
 
   debugger
-  throw new Error(`Unknown node ${JSON.stringify(node)}`)
+  throw new Error(`Unknown node ${stringify node}`)
 
 export default gen
 

source/parser.hera

@@ -2740,6 +2740,22 @@ RangeExpression
       end: e,
     }
 
+  # NOTE: [x..] range to infinity, valid only in for loops
+  ExtendedExpression:s __:ws DotDot &( __ CloseBracket ) ->
+    return {
+      type: "RangeExpression",
+      children: ["[]", {
+        type: "Error",
+        message: "Infinite range [x..] is only valid in for loops",
+      }],
+      start: s,
+      end: {
+        type: "Identifier",
+        name: "Infinity",
+        children: ["Infinity"],
+      },
+    }
+
 ArrayLiteralContent
   RangeExpression
   # NOTE: No longer need to special-case implicit object literals separated

source/parser/for.civet

@@ -25,10 +25,15 @@ function forRange(
 
   counterRef := makeRef("i")
 
+  //infinite := if {type: "Identifier", name: "Infinity"} := end then true
+  infinite := end.type is "Identifier" and end.name is "Infinity"
+
   let stepRef
   if stepExp
     stepExp = insertTrimmingSpace(stepExp, "")
     stepRef = maybeRef(stepExp, "step")
+  else if infinite
+    stepExp = stepRef = "1"
 
   startRef .= maybeRef(start, "start")
   endRef .= maybeRef(end, "end")
@@ -75,17 +80,19 @@ function forRange(
     ? [counterRef, " <= ", endRef, " : ", counterRef, " >= ", endRef]
     : [counterRef, " < ", endRef, " : ", counterRef, " > ", endRef]
 
-  condition := stepRef
+  condition := infinite ? [] : stepRef
     ? [stepRef, " !== 0 && (", stepRef, " > 0 ? ", ...counterPart, ")"]
     : ascRef
       ? [ascRef, " ? ", ...counterPart]
       : asc ? counterPart.slice(0, 3) : counterPart.slice(4)
 
-  increment := stepRef
-    ? [...varAssign, counterRef, " += ", stepRef]
-    : ascRef
-      ? [...varAssign, ascRef, " ? ++", counterRef, " : --", counterRef]
-      : [...varAssign, asc ? "++" : "--", counterRef]
+  increment := infinite
+    ? [...varAssign, "++", counterRef]
+    : stepRef
+      ? [...varAssign, counterRef, " += ", stepRef]
+      : ascRef
+        ? [...varAssign, ascRef, " ? ++", counterRef, " : --", counterRef]
+        : [...varAssign, asc ? "++" : "--", counterRef]
 
   return {
     declaration,

test/for.civet

@@ -146,6 +146,18 @@ describe "for", ->
     }
   """
 
+  testCase """
+    infinite range
+    ---
+    for i of [1..]
+      console.log(i)
+    ---
+    for (let i1 = 1; ; ++i1) {
+      const i = i1;
+      console.log(i)
+    }
+  """
+
   testCase """
     range without declaration
     ---
@@ -179,6 +191,23 @@ describe "for", ->
     }
   """
 
+  testCase """
+    infinite range without declaration
+    ---
+    for [1..]
+      console.log("hello")
+    ---
+    for (let i = 1; ; ++i) {
+      console.log("hello")
+    }
+  """
+
+  throws """
+    infinite range without for
+    ---
+    [1..]
+  """
+
   testCase """
     for of character range
     ---