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bc7d5386ef
- visit_ was producing problematic results, because it visits every
subexpression. This means that for:
f x y z
it visits all of:
f x y z, f x y, f x, f
But, if we take prefixes for all of those, we'll always end up
eliminating only one variable, even if more are redundant.
- Instead of the above, use `visit` with a recursive procedure. This
requires some other modifications, because we need to manually recurse
into arguments of applied functions that aren't variables.
- Added a test case for the above trickiness
- Prefix should have been a newtype
1.1 KiB
1.1 KiB
.> builtins.merge
Tests cases that produced bad decompilation output previously. There are three cases that need to be 'fixed up.'
- lambda expressions with free variables need to be beta reduced
- let defined functions need to have arguments removed and occurrences rewritten.
- let-rec defined functions need to have arguments removed, but it is a more complicated process.
> Any (w x -> let
f0 y = match y with
0 -> x
n -> 1 + f1 (drop y 1)
f1 y = match y with
0 -> w + x
n -> 1 + f0 (drop y 1)
f2 x = f2 x
f3 y = 1 + y + f2 x
g h = h 1 + x
g (z -> x + f0 z))
Also check for some possible corner cases.
f should not have its x argument eliminated, because it doesn't
always occur with x as the first argument, but if we aren't careful,
we might do that, because we find the first occurrence of f, and
discard its arguments, where f also occurs.
> Any (x -> let
f x y = match y with
0 -> 0
_ -> f x (f y (drop y 1))
f x 20)