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102 lines
2.7 KiB
Nim
102 lines
2.7 KiB
Nim
discard """
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description: '''IC vs `nim c`: closure environments, their hooks and their owners'''
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"""
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#? metamorphic
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# A closure's environment type — and the `=destroy`/`=copy` the compiler lifts
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# for it — is minted by the BACKEND, during the `lower` stage, and exists in no
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# module's semmed NIF. The per-module backend has to decide which translation
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# unit emits such a routine, and the owner walk it uses lands on the module of
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# the ORIGINAL generic: for a generic closure iterator defined in one module and
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# instantiated in another, that is a module which never sees the instance, so the
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# env's `=destroy` was emitted by nobody (`undefined reference to
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# eqdestroy__c485__…`). Every referencing TU emits it now.
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#
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# The steps then move the captured state around, because the env's LAYOUT is what
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# decides whether those hooks are trivial: a body-only edit that adds a capture
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# changes the env type of a routine whose importers do not re-sem.
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#!FILE clleaf.nim
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type Ev* = proc (s: string): string {.closure.}
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proc leafMaker*(tag: string): Ev =
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var n = 0
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proc outer(s: string): string =
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proc inner(t: string): string =
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inc n
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tag & ":" & t & ":" & $n
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inner(s)
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result = outer
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iterator leafIter*[T](xs: seq[T]): T {.closure.} =
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for x in xs: yield x
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#!FILE clmid.nim
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import clleaf
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proc midMaker*(tag: string): Ev =
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let base = leafMaker(tag & "/mid")
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var calls = 0
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result = proc (s: string): string =
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inc calls
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base(s) & "#" & $calls
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proc midIter*(): seq[string] =
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# instantiates `leafIter[string]` HERE, not where it is defined
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result = @[]
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for x in leafIter(@["p", "q"]): result.add x
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#!FILE main.nim
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import clleaf, clmid
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let t = midMaker("top")
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echo t("Alpha")
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echo t("Beta")
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echo midIter()
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# an instance only the main module has
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var fs: seq[float] = @[]
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for x in leafIter(@[1.5, 2.5]): fs.add x
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echo fs
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#!STEP
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# body-only edit that GROWS the environment: a second captured local
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#!FILE clleaf.nim
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type Ev* = proc (s: string): string {.closure.}
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proc leafMaker*(tag: string): Ev =
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var n = 0
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var seen: seq[string] = @[]
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proc outer(s: string): string =
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proc inner(t: string): string =
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inc n
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seen.add t
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tag & ":" & t & ":" & $n & ":" & $seen.len
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inner(s)
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result = outer
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iterator leafIter*[T](xs: seq[T]): T {.closure.} =
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var i = 0
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for x in xs:
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inc i
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yield x
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#!STEP
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# and shrink it again
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#!FILE clleaf.nim
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type Ev* = proc (s: string): string {.closure.}
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proc leafMaker*(tag: string): Ev =
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var n = 0
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proc outer(s: string): string =
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proc inner(t: string): string =
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inc n
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tag & ":" & t & ":" & $n
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inner(s)
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result = outer
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iterator leafIter*[T](xs: seq[T]): T {.closure.} =
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for x in xs: yield x
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#!STEP
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