add decompose, deopcompose

.github/workflows/ci.yml

@@ -12,6 +12,7 @@ jobs:
           - '1.0'
           - '1.4'
           - '1.5.0-beta1'
+          - '1.6'
           - 'nightly'
         os:
           - ubuntu-latest

Project.toml

@@ -1,7 +1,7 @@
 name = "CompositionsBase"
 uuid = "a33af91c-f02d-484b-be07-31d278c5ca2b"
 authors = ["Takafumi Arakaki <[email protected]> and contributors"]
-version = "0.1.1-DEV"
+version = "0.1.1"
 
 [compat]
 julia = "1"

src/CompositionsBase.jl

@@ -36,4 +36,48 @@ The opposite composition operator defined as
 export ∘, compose, opcompose
 @eval export $(Symbol("⨟"))  # for Julia 1.0
 
+if isdefined(Base, :ComposedFunction)
+    export decompose, deopcompose
+    """
+        decompose(comp)
+
+    Destructure a composition into its pieces:
+    ```jldoctest
+    julia> using CompositionsBase
+
+    julia> decompose(sin ∘ cos)
+    (sin, cos)
+
+    julia> decompose(sin∘cos∘identity)
+    (sin, cos, identity)
+
+    julia> decompose(sin)
+    (sin,)
+    ```
+
+    Requires at least Julia version 1.6. See also [deopcompose](@ref).
+    """
+    decompose(f) = (f,)
+    decompose(o::Base.ComposedFunction) = (decompose(o.outer)..., decompose(o.inner)...)
+
+    """
+        deopcompose(comp)
+
+    Destructure a composition into its pieces:
+    ```jldoctest
+    julia> using CompositionsBase
+
+    julia> deopcompose(sin ⨟cos⨟tan)
+    (sin, cos, tan)
+
+    julia> decompose(sin⨟cos⨟tan)
+    (tan, cos, sin)
+    ```
+
+    Requires at least Julia version 1.6. See also [decompose](@ref).
+    """
+    deopcompose(f) = (f,)
+    deopcompose(o::Base.ComposedFunction) = (deopcompose(o.inner)..., deopcompose(o.outer)...)
+end
+
 end # module

test/runtests.jl

@@ -18,5 +18,19 @@ end
 if VERSION >= v"1.5.0-DEV.302"  # for ⨟
     include("test_julia15.jl")
 end
+if VERSION >= v"1.6"
+    @testset "decompose, deopcompose" begin
+        @test decompose(sin) === (sin,)
+        @test decompose(sin∘cos) === (sin,cos)
+        @test decompose(sin∘cos∘ tan) === (sin,cos,tan)
+        @test decompose((sin∘cos)∘ tan) === (sin,cos,tan)
+        @test decompose(sin∘(cos∘ tan)) === (sin,cos,tan)
+        @test decompose((sqrt∘sin)∘(cos∘ tan)) === (sqrt,sin,cos,tan)
+
+        @test deopcompose((sqrt∘sin)∘(cos∘ tan)) === (tan,cos,sin,sqrt)
+        @inferred deopcompose((sqrt∘sin)∘(cos∘ tan))
+        @inferred decompose((sqrt∘sin)∘(cos∘ tan))
+    end
+end
 
 end  # module