add Splat (#785)

Project.toml

@@ -1,6 +1,6 @@
 name = "Compat"
 uuid = "34da2185-b29b-5c13-b0c7-acf172513d20"
-version = "4.4.0"
+version = "4.5.0"
 
 [deps]
 Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"

README.md

@@ -70,6 +70,8 @@ changes in `julia`.
 
 ## Supported features
 
+* `Splat(f)` which is equivalent to `args -> f(args...)`. ([#42717]) (since Compat 4.5.0) 
+
 * `Compat.@assume_effects setting... ex` overrides the compiler's effect modeling for the method definition `ex` on Julia versions that support this feature. Julia version without support just pass back `ex`. ([#43852]) (since Compat 4.4.0)
 
 * `div`, `lcm`, `gcd`, `/`, `rem`, and `mod` will `promote` heterogenous `Dates.Period`s ([`@bdf9ead9`]). (since Compat 4.3.0)

src/Compat.jl

@@ -616,6 +616,44 @@ if VERSION < v"1.9.0-DEV.1163"
 
     _empty_stack(_...) = throw(ArgumentError("`stack` on an empty collection is not allowed"))
 end
+
+@static if VERSION < v"1.9.0-DEV.513"
+    # https://github.com/JuliaLang/julia/pull/42717
+    export Splat
+
+    struct Splat{F} <: Function
+        f::F
+        Splat(f) = new{Core.Typeof(f)}(f)
+    end
+
+    (s::Splat)(args) = s.f(args...)
+    Base.print(io::IO, s::Splat) = print(io, "Splat(", s.f, ')')
+    Base.show(io::IO, s::Splat) = print(io, s)
+    Base.show(io::IO, ::MIME"text/plain", s::Splat) = show(io, s)
+    @doc """
+    Splat(f)
+Equivalent to
+```julia
+    my_splat(f) = args->f(args...)
+```
+i.e. given a function returns a new function that takes one argument and splats
+its argument into the original function. This is useful as an adaptor to pass
+a multi-argument function in a context that expects a single argument, but
+passes a tuple as that single argument. Additionally has pretty printing.
+# Example usage:
+```jldoctest
+julia> map(Base.Splat(+), zip(1:3,4:6))
+3-element Vector{Int64}:
+ 5
+ 7
+ 9
+julia> my_add = Base.Splat(+)
+Splat(+)
+julia> my_add((1,2,3))
+6
+```
+""" Splat
+end 
 
 include("deprecated.jl")
 

test/runtests.jl

@@ -577,3 +577,9 @@ end
         @test op(xms, yms) == op(xms, ys) == op(xs, yms)
     end
 end
+
+@testset "Splat" begin
+    @test Splat(+)((1,2,3)) == 6
+    @test repr(Splat(+)) == "Splat(+)"
+    @test repr(MIME"text/plain"(), Splat(+)) == "Splat(+)"
+end