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e83f27e6a0
* out parameters: enforce that 'out' is only used as a parameter * make tables.nim use 'out' parameters * better backwards compat
39 lines
931 B
Nim
39 lines
931 B
Nim
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#
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# Nim's Runtime Library
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# (c) Copyright 2022 Nim contributors
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#
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# See the file "copying.txt", included in this
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# distribution, for details about the copyright.
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#
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## `outParamsAt` macro for easy writing code that works with both 2.0 and 1.x.
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import macros
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macro outParamsAt*(positions: static openArray[int]; n: untyped): untyped =
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## Use this macro to annotate `out` parameters in a portable way.
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runnableExamples:
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proc p(x: var int) {.outParamsAt: [1].} =
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discard "x is really an 'out int' if the Nim compiler supports 'out' parameters"
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result = n
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when defined(nimHasOutParams):
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var p = n.params
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for po in positions:
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p[po][^2].expectKind nnkVarTy
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p[po][^2] = newTree(nnkOutTy, p[po][^2][0])
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when isMainModule:
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{.experimental: "strictDefs".}
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proc main(x: var int) {.outParamsAt: [1].} =
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x = 3
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proc us =
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var x: int
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main x
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echo x
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us()
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