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
Sincerely,
Ken Hamada
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