ForExpr

(Difference between revisions)

Revision as of 10:07, 20 April 2011

ForExpr is a nonkernel node which executes code for each element in a collection or other object implementing iterate/1.

"for" (optKeyPattern "=>")? valuePattern "in" collection "{" body "}" ({optBreakCatch an EMatcher}: "catch" pattern "{" expr "}")?

XXX We need to formalize the grammar definitions used in our spec

XXX Define the expansion of ForExpr

collection may not use nouns bound by optKeyPattern or valuePattern, or vice versa.

C9KOXf Got it! Thanks a lot again for hlepnig me out!

@@ Line 21: / Line 21: @@
 * <var>collection</var> may not use nouns bound by <var>optKeyPattern</var> or <var>valuePattern</var>, or vice versa.
-== Tests ==
+C9KOXf Got it! Thanks a lot again for hlepnig me out!
-The function provided to (the value of <var>collection</var>)'s [[:Category:Message iterate/1|iterate/1]] method throws if called after iterate/1 has returned.
- ? var captured := null
- ? def capturer {
- >   to iterate(f) :void {
- >     captured := f
- >     f("a", "b")
- >   }
- > }
- # value: <capturer>
- ? for x => y in capturer { println(x, " -> ", y) }
- # stdout: a -> b
- #
- ? captured("c", "d")
- # problem: For-loop body isn't valid after for-loop exits.
-The return value of iterate/1 is not the return value of the for loop; the loop returns [[null]] unless a return value is given by [[__break]].
- ? def confuser extends [1,2,3] {
- >   to iterate(f) {
- >     super.iterate(f)
- >     return __Portrayal
- >   }
- > }
- # value: <confuser>
- ? def optKeyOf(collection, toFind) {
- >   return for key => val in collection {
- >     if (val == toFind) {
- >       break key
- >     }
- >   }
- > }
- ? optKeyOf(confuser, 1)
- # value: 0
- ? [optKeyOf(confuser, 43)]
- # value: [null]
-[[Category:E language specification]]
-[[Category:Nonkernel-E nodes]]