2016-07-19 17:56 GMT+03:00 Bram Moolenaar <[email protected]>:
>
> 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).
Space is OK if “function” is an identifier (variable or function
name). E.g. `echo string (5)` displays `5`, `let String = function
('string') | echo String (5)` also is OK. But, I guess, fixing this
will make some :echo calls fail.
>
>> BTW, I will update the tests later.
>
> Thanks, will look at it then.
>
> --
> [clop clop]
> MORTICIAN: Who's that then?
> CUSTOMER: I don't know.
> MORTICIAN: Must be a king.
> CUSTOMER: Why?
> MORTICIAN: He hasn't got shit all over him.
> The Quest for the Holy Grail (Monty Python)
>
> /// Bram Moolenaar -- [email protected] -- http://www.Moolenaar.net \\\
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