Hi,
2016/7/18 Mon 11:26:23 UTC+9 Ken Takata wrote:
> Hi,
>
> 2016/7/17 Sun 21:26:29 UTC+9 itchyny wrote:
> > I additionally submit another test case.
> >
> > let Y = {f -> (({x -> f ({y -> x(x)(y)})}) ({x -> f ({y -> x(x)(y)})}))}
> > let Fact = {f -> {x -> (x == 0 ? 1 : x * f(x - 1))}}
> > echo Y(Fact)(5)
> >
> > I expect this script prints 120 but I got E110: Missing ')' in 7.4.2049
> > (and also with the experimental patch).
> > Is there something wrong with the above code or is there some bug in the
> > parsing code in eval.c?
> >
> > Here are the counterparts in Python
> > Y = lambda f: (lambda x: f (lambda y: x(x)(y))) (lambda x: f (lambda y:
> > x(x)(y)))
> > Fact = lambda f: lambda x: (1 if x == 0 else x * f(x - 1))
> > print Y(Fact)(5)
> >
> > and in JavaScript
> > var Y = function(f){ return (function(x){ return f (function(y){ return
> > x(x)(y); }); }) (function(x){ return f (function(y){ return x(x)(y); });
> > }); };
> > var Fact = function(f){ return function(x){ return (x == 0 ? 1 : x * f(x -
> > 1)); }; };
> > console.log(Y(Fact)(5));
> >
> > reference:
> > https://en.wikipedia.org/wiki/Lambda_calculus#Recursion_and_fixed_points,
> > https://en.wikipedia.org/wiki/Fixed-point_combinator#Fixed_point_combinators_in_lambda_calculus
>
> I have updated the patch for the latest code:
> https://bitbucket.org/k_takata/vim-ktakata-mq/src/006cdbbeef26201154d04b7dfe1aed119321acb1/lambda-update.patch?at=default
>
> The SEGV on test_alot.vim seems fixed.
>
>
> > let Y = {f -> (({x -> f ({y -> x(x)(y)})}) ({x -> f ({y -> x(x)(y)})}))}
>
> This still causes errors. Not sure why. Simpler example would be better.
I have updated the patch:
https://bitbucket.org/k_takata/vim-ktakata-mq/src/29d0a0ecfa23f70852fa3f5c33e15ea629cd17b4/lambda-update.patch?fileviewer=file-view-default
Now lambda expressions can access outer arguments. E.g.:
:function Foo(arg)
: return {x -> x + a:arg}
:endfunction
:let Bar = Foo(5)
:echo Bar(2)
7
And now I disable the "a:" prefix for the lambda's arguments:
:function Foo(arg)
: return {x -> a:x + a:arg} " Error
:endfunction
"a:" is now used for outer arguments only.
> > let Y = {f -> (({x -> f ({y -> x(x)(y)})}) ({x -> f ({y -> x(x)(y)})}))}
> > let Fact = {f -> {x -> (x == 0 ? 1 : x * f(x - 1))}}
> > echo Y(Fact)(5)
The above doesn't work, but the following works now:
:let Y = {f -> (({x -> f ({y -> x(x)(y)})})({x -> f ({y -> x(x)(y)})}))}
:let Fact = {f -> {x -> (x == 0 ? 1 : x * f(x - 1))}}
:echo Y(Fact)(5)
120
The difference is a space between a lambda expression and its arguments.
A similar example is here:
let x = function('sin') (1) " E15
let x = function('sin')(1) " OK
I'm not sure this is intended.
BTW, I will update the tests later.
Regards,
Ken Takata
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