cps: experimental support for for-loops #84
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disruptek
requested changes
May 3, 2021
cps.nim
Outdated
| n[1] = getTypeInst n[2] | ||
| else: | ||
| # get the type from the symbol as the last resort. | ||
| # walkaround for #48. |
| @@ -854,13 +870,21 @@ proc cpsXfrm(T: NimNode, n: NimNode): NimNode = | |||
| result = copy n | |||
| result = workaroundRewrites(result) | |||
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| macro cps*(T: typed, n: typed): untyped = | |||
| macro cps2(T: typed, n: typed): untyped = | |||
| # I hate doing stuff inside macros, call the proc to do the work | |||
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Suggested change
| # I hate doing stuff inside macros, call the proc to do the work | |
| ## We used `getImplTransformed` to make a pre-pass whatfer transforming `for` and `defer` | |
| ## into the input to this macro, where we perform the meat of the CPS transform. |
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I think we could use a for loop macro to remove part of the getImplTransformed dependency, I still need to think about the defer one.
Not a blocker
Comment on lines
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| when defined(nimdoc): | ||
| result = n | ||
| else: | ||
| result = cpsXfrm(T, n) |
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This when should move into cps().
| # I hate doing stuff inside macros, call the proc to do the work | ||
| when defined(nimdoc): | ||
| result = n | ||
| else: | ||
| result = cpsXfrm(T, n) | ||
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| macro cps*(T: typed, n: typed): untyped = |
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Suggested change
| macro cps*(T: typed, n: typed): untyped = | |
| macro cps*(T: typed, n: typed): untyped = | |
| ## Rewrite procedure `n` in Continuation-Passing Style, extending type `T` to store any transient locals. |
saem
approved these changes
May 4, 2021
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Noted the for loop macro idea for posterity. @disruptek already highlighted the doc bits, lgtm.
For-loops are inlined using block statements, which messes with their control flow due to nim-works#76. Breaks a test in tzevv due to defer being rewritten into try-finally, which doesn't work. Co-authored-by: Andy Davidoff <github@andy.disruptek.com>
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Rebased, compiler issues that I found:
case true
of true:
echo "true"
of false:
echo "failed"transformed to: case true
of true:
echo "true"
of false:
echo "failed"
else:
nilAnd this stuff don't pass sem, obviously.
a & b & ctransformed to And it also doesn't pass sem because a I'd say we should perform this transform ourselves. |
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For-loops are inlined using block statements, which messes with their
control flow due to #76.
Breaks "for loop with continue, break" test. On the flip side,
splitting now functions on them.
Also breaks a test in tzevv due to defer being rewritten into
try-finally, which doesn't work due to #80.