## ChainedFixes.jl

Chain Julias's in fix operators
Author Tokazama
Popularity
9 Stars
Updated Last
9 Months Ago
Started In
April 2020

# ChainedFixes

ChainedFixes.jl provides useful tools for interacting with functions where arguments are fixed to them.

## The or, and methods

Some simple functionality available form this package is chaining any fixed function.

julia> using ChainedFixes

julia> gt_or_lt = or(>(10), <(5))
or(>(10), <(5))

julia> gt_or_lt(2)
true

julia> gt_or_lt(6)
false

julia> gt_and_lt = and(>(1), <(5))
and(>(1), <(5))

julia> gt_and_lt(2)
true

julia> gt_and_lt(0)
false

There's more convenient syntax for these available in the Julia REPL.

julia> gt_or_lt = >(10) ⩔ <(5); # \Or<TAB>

julia> gt_or_lt(2)
true

julia> gt_or_lt(6)
false

julia> gt_and_lt = >(1) ⩓ <(5); # \And<TAB>

julia> gt_and_lt(2)
true

julia> gt_and_lt(0)
false

## Creating new fixed methods with @nfix

Any function can have methods fixed to it with @nfix.

julia> fxn1(x::Integer, y::AbstractFloat, z::AbstractString) = Val(1);

julia> fxn1(x::Integer, y::AbstractString, z::AbstractFloat) = Val(2);

julia> fxn1(x::AbstractFloat, y::Integer, z::AbstractString) = Val(3);

julia> fxn2(; x, y, z) = fxn1(x, y, z);

julia> fxn3(args...; kwargs...) = (fxn1(args...), fxn2(; kwargs...));

julia> f = @nfix fxn1(1, 2.0, _)
fxn1(1, 2.0, _1)

julia> f("a")
Val{1}()

julia> f = @nfix fxn1(1, _, 2.0)
fxn1(1, _1, 2.0)

julia> f("a")
Val{2}()

julia> f = @nfix fxn1(1.0, _, "")
fxn1(1.0, _1, "")

julia> f(2)
Val{3}()

julia> f = @nfix fxn2(x=1, y=2.0)
fxn2(; x = 1, y = 2.0)

julia> f(z = "a")
Val{1}()

julia> f = @nfix fxn2(x=1, z=2.0)
fxn2(; x = 1, z = 2.0)

julia> f(y = "a")
Val{2}()

julia> f = @nfix fxn3(1, 2.0, _; x = 1.0, z= "")
fxn3(1, 2.0, _1; x = 1.0, z = "")

julia> f(""; y = 1)
(Val{1}(), Val{3}())

If we specify the underscore suffix we arguments can be repeated within a single function.

julia> f = @nfix *(_1, _1)
*(_1, _1)

julia> f(2)
4

## Chaining piped methods

We can create a chain a functions that act like an uncalled pipe (e.g., |>). A chain of fixed functions can be chained together via pipe_chain.

julia> f = pipe_chain(@nfix(_ * "is "), @nfix(_ * "a "), @nfix(_ * "sentence."))
|> *(_1, "is ") |> *(_1, "a ") |> *(_1, "sentence.")

julia> f("This ")
"This is a sentence."

julia> f2 = pipe_chain(f, endswith("sentence."))
|> *(_1, "is ") |> *(_1, "a ") |> *(_1, "sentence.") |> endswith("sentence.")

julia> f2("This ")
true

julia> f2 = pipe_chain(f, startswith("This"))
|> *(_1, "is ") |> *(_1, "a ") |> *(_1, "sentence.") |> startswith("This")

julia> f2("This ")
true

julia> f = pipe_chain(and(<=(3), !=(2)), ==(true), in(trues(2)), !in(falses(2)), >=(true))
|> and(<=(3), !=(2)) |> ==(true) |> in(Bool[1, 1]) |> !in(Bool[0, 0]) |> >=(true)

julia> f(1)
true

julia> f = pipe_chain(isapprox(0.1), !isapprox(0.2))
|> (0.1) |> !(0.2)

julia> f(0.1 - 1e-10)
true

Internally, this includes support for those found in Julia's Base module (Base.Fix1, Base.Fix2) and from ChainedFixes (ChainedFix and NFix).

## Constants

The constants on the right sight of the following table may be exported and accessed via using ChainedFixes.ChainedCore The syntax corresponding to each constant is on the left.

Syntax Type Constant
pipe_chain(f1, f2) PipeChain{F1,F2}
and(f1::F1, f1::F2)/⩓(f1::F1, f1::F2) And{F1,F2}
or(f1::F1, f1::F2)/⩔(f1::F1, f1::F2) Or{F1,F2}
isapprox(x::T; kwargs::Kwargs) Approx{T,Kwargs}
!isapprox(x::T; kwargs::Kwargs) NotApprox{T,Kwargs}
in(x::T) In{T}
!in(x::T) NotIn{T}
<(x::T) Less{T}
<=(x::T) LessThanOrEqual{T}
>(x::T) Greater{T}
>=(x::T) GreaterThanOrEqual{T}
==(x::T) Equal{T}
isequal(x::T) Equal{T}
!=(x::T) NotEqual{T}
startswith(x::T) StartsWith{T}
endswith(x::T) EndsWith{T}

## Combining fixed methods

The real utility of ChainedFixes is when combining fixed methods in creative ways

julia> splat_pipe(op, args::Tuple) = op(args...);

julia> splat_pipe(op) = @nfix splat_pipe(op, _...);

julia> f = pipe_chain(extrema, splat_pipe(+))
|> extrema |> splat_pipe(+, _...)

julia> f([1 2; 3 4])
5