ForExpr - Revision history

Kevin Reid: revert

2011-04-20T18:44:48Z

revert

New page

[[ForExpr]] is a [[nonkernel]] node which executes code for each element in a collection or other object implementing [[:Category:Message iterate/1|iterate/1]].

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

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

== Fields ==

* <var>optKeyPattern</var> :[[nullOk]]<nowiki>[</nowiki>[[Pattern]]]
* <var>valuePattern</var> :[[Pattern]]
* <var>collection</var> :[[nullOk]]<nowiki>[</nowiki>[[EExpr]]]
* <var>body</var> :[[EExpr]]
* <var>optBreakCatch</var> :[[nullOk]]<nowiki>[</nowiki>[[EMatcher]]]

== Expansion ==

{{XXX|Define the expansion of ForExpr}}

== Static constraints ==

* <var>collection</var> may not use nouns bound by <var>optKeyPattern</var> or <var>valuePattern</var>, or vice versa.

== Tests ==

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]]

89.248.248.152: /* Static constraints */

2011-04-20T13:22:40Z

Static constraints

←Older revision		Revision as of 13:22, 20 April 2011
Line 17:		Line 17:
	{{XXX\|Define the expansion of ForExpr}}		{{XXX\|Define the expansion of ForExpr}}

-	~~== Static constraints ==~~	+	Kudos! What a neat way of thnkiing about it.
-		+
-	* <var>collection</var> may not use nouns bound by <var>optKeyPattern</var> or <var>valuePattern</var>, or vice versa.	+
-		+
-	~~C9KOXf Got it~~! ~~Thanks~~ a ~~lot again for hlepnig me out!~~	+

203.92.44.228: /* Tests */

2011-04-20T10:07:12Z

Tests

←Older revision		Revision as of 10:07, 20 April 2011
Line 21:		Line 21:
	* <var>collection</var> may not use nouns bound by <var>optKeyPattern</var> or <var>valuePattern</var>, or vice versa.		* <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]]~~	+

Kevin Reid at 21:48, 14 May 2009

2009-05-14T21:48:05Z

←Older revision

Revision as of 21:48, 14 May 2009