fixes #7187 sequtils.toSeq produces the sequence from the iterator twice #8586
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timotheecour
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This was referenced Aug 9, 2018
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Varriount
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Aug 11, 2018
lib/pure/collections/sequtils.nim
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| @@ -497,9 +513,10 @@ template toSeq*(iter: untyped): untyped = | |||
| ## assert odd_numbers == @[1, 3, 5, 7, 9] | |||
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| when compiles(iter.len): | |||
| evalOnce(t_D20180808T230638, iter, letAssigneable = true) | |||
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What's with the symbol name?
lib/pure/collections/sequtils.nim
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| @@ -25,6 +25,22 @@ import macros | |||
| when not defined(nimhygiene): | |||
| {.pragma: dirty.} | |||
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| macro evalOnce(v, exp: untyped, letAssigneable: static[bool]): untyped = | |||
| expectKind(v, nnkIdent) | |||
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What does this do different from a single 'let' statement?
timotheecour
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timotheecour
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Aug 16, 2018
| @@ -1106,16 +1122,12 @@ when isMainModule: | |||
| doAssert newSeq[int](0).mapIt(it) == @[] | |||
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| block: # mapIt redifinition check, see https://github.com/nim-lang/Nim/issues/8580 | |||
| let t = [1,2].mapIt(it) | |||
| doAssert t == @[1,2] | |||
| let s2 = [1,2].mapIt(it) | |||
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s2 is correct here as test case for #8580 since implementation of mapIt now uses s2, not t.
timotheecour
commented
Aug 16, 2018
| doAssert getInput().mapIt(it*2).mapIt(it*10) == @[20, 40] | ||
| # make sure argument evaluated only once, analog to | ||
| counter = 0 | ||
| doAssert [1,2].identity().mapIt(it*2).mapIt(it*10) == @[20, 40] |
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simplifies test case, reusing identity and counter, as done in other test cases in this file
timotheecour
commented
Aug 16, 2018
| template foo2(x: openArray[int]): seq[int] = x.mapIt(it * 10) | ||
| counter = 0 | ||
| doAssert foo2(openArray[int]([identity(1),identity(2)])) == @[10,20] | ||
| # TODO: this fails; not sure how to fix this case | ||
| # doAssert counter == 2 | ||
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| counter = 0 | ||
| doAssert openArray[int]([identity(1), identity(2)]).mapIt(it) == @[1,2] | ||
| # ditto |
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added corner test case similar to the one just above
timotheecour
commented
Aug 16, 2018
| inc i | ||
| result | ||
| block: | ||
| evalOnceAs(iter2, iter, true) |
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see #8584 for why we need evalOnceAs
timotheecour
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@Varriount PTAL |
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@Araq could we please merge this? I have other PR's coming up depending on this |
PMunch
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Aug 17, 2018
…rator twice (nim-lang#8586) * cleanups refs nim-lang#8584 * fixes nim-lang#7187
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NOTE: this PR depends on #8584 which should be merged first