Pipe operation to function left-to-right

[DiermenSoftware]

Currently this is the result of the pipe operator:

function = (str1,str2,str3) => str1 + " " + str2 + " " + str3;
function("1","2","3"); //returns: "1 2 3"
"1"|function("2","3"); //returns: "2 3 1"  desired: "1 2 3"

Would it be possible to optionally change this behaviour in the library settings so that the left statement is injected into the first parameter of a function?

[FlorianRappl]

Hm that is independent of the Pipe operator. I think what you are looking for is changing the behavior of currying in MAGES.

Currying states that f(x,y,z) = f(x)(y)(z), such that g(z)=f(x, y).

(See: https://github.com/FlorianRappl/Mages/blob/devel/doc/language.md#auto-currying)

What we could think about is to introduce a syntax such as _ to denote where missing arguments should be inserted:

"1" | function(_, "2", "3") // returns "1 2 3"
"2" | function("1", _, "3") // returns "1 2 3"
function("1", _, "3") // returns a new function with one parameter, aliasing g(x) = function("1", x, "3")

Such a language extension could be useful on other locations, too. What are your thoughts?

[DiermenSoftware]

This would be a nice option, however the built-in functions still work in the same way.
The currying is indeed the way to make it work more like C# logic for example:

1.123|round(1);  // should be 1.1
round(1.123, 1); // should be 1.1
10|sub(2); // should be 10-2
sub(10, 2); // should be 10-2

Than probably the order of those functions need to be swapped.

[FlorianRappl]

Yeah we don't want to change the currying and for technical reasons you cannot go from left-sided to right-sided (as a matter of fact for most / some functions we don't know "when" the upper bound of arguments ends, i.e., if you have f(x, y, z) but f already returns something useful for f(x, y) then you cannot eat arguments from the right).

So the only reliable way is from the left.

I actually think that the _ (leave the argument open) operator is what we need here. It would solve

2 | sub(_, 10) // would be sub(2, 10) = 10-2
2 | sub(10) // would be sub(10, 2) = 2-10

quite elegantly imho.

[FlorianRappl]

Pushed an implementation of the placeholder parameter - available in the preview version.

[DiermenSoftware]

You are right, this is indeed a very elegant solution that also makes the piping more flexible.
Thanks!