Ken Takata wrote:
> 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.
Yes, there should not be a space between the function and the (args).
> BTW, I will update the tests later.
Thanks, will look at it then.
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