Expression-based pipe operators with placeholder argument for Nim.
Nim already has a nice syntax sugar called "Universal Call Syntax" or UCS that lets you call procedures on arguments with the popular 'dot' notation of other object-oriented languages. So this already acts like a simple chaining pipe operator for functions with first argument on the left-hand side:
proc plus20(arg0: int): int = arg0 + 20
proc plus(arg0, x: int): int = arg0 + x
let a = 10 . plus20
10 . plus20 . echo
10 . plus20 . plus20() . echo
10 . plus(20) . echo
10 . plus(30) . plus(40) . echoHowever you can't use this syntax if you want to pipe into procs on arguments other than the first one.
With pipexp you can still use a UCS syntax, but also
use a placeholder "_" argument where the return of
the previous pipe is inserted to:
I don't know if I'll keep | as the operator, it's still early
import pipexp
proc plus20(arg0: int): int = arg0 + 20
proc plus_a0(arg, x: int): int = arg + x
proc plus_a1(x, arg: int): int = arg + x
let a = 10 | plus20
10 | plus20 | echo
10 | plus20 | plus20() | plus20(_) | echo
10 | plus_a0(20) | echo
10 | plus_a0(_,20) | echo
10 | plus_a1(20,_) | echo
10 | plus_a1(30,_) | plus_a1(40,_) | echo
# You can pass multiple placeholders:
proc plus_as(a1, a2, a3: int): int = a1 + a2 + a3
10 | plus_as(_,_,50) | echo
10 | plus_as(90,_,_) | echo
10 | plus_as(_,_,_) | echo
# You can pass lambdas if they are enclosed by curly brackets or parentheses:
10 | {
proc(x: int): int =
x + 20
} | echo
# You can index the placeholder
[10,20] | plus20(_[1]) | echo
[10,20] | plus20(_[0]) | echo
# You can call the placeholder
plus20 | plus20(_(10)) | echoYou can also make use of a pipeline macro called pipe to
separate the callables in different lines:
let b = pipe(10, plus20)
pipe(10, plus20, echo)
pipe(10, plus20, plus20(), plus20(_), echo)
pipe(10, plus_a1(30,_), plus_a1(40,_), echo)
let c = pipe 10:
plus20
plus_a0(40)
plus_a1(30,_)
{
proc (_: int): int =
_ + 50
}- Support anonymous procs
- Nim native lambdas
-
=>anonymous procs fromstd/sugar
- Other features like Pipe.jl
- Indexing placeholder
- Unpacking placeholder
- Calling placeholder
- Allow configuring the placeholder symbol
- Allow multiple instances of "
_"
Maybe:
- Other operators like magrittr