Support 2-arg argmin/argmax/findmin/findmax

xref JuliaLang/julia#35316

Author: timholy

Project.toml

@@ -1,6 +1,6 @@
 name = "Compat"
 uuid = "34da2185-b29b-5c13-b0c7-acf172513d20"
-version = "3.25.0"
+version = "3.26.0"
 
 [deps]
 Base64 = "2a0f44e3-6c83-55bd-87e4-b1978d98bd5f"

src/Compat.jl

@@ -859,6 +859,24 @@ if VERSION < v"1.2.0-DEV.246"
     end
 end
 
+if VERSION < v"1.7.0-DEV.119"
+    # Part of https://github.com/JuliaLang/julia/pull/35316
+    isunordered(x) = false
+    isunordered(x::AbstractFloat) = isnan(x)
+    isunordered(x::Missing) = true
+
+    isgreater(x, y) = isunordered(x) || isunordered(y) ? isless(x, y) : isless(y, x)
+
+    Base.findmax(f, domain) = mapfoldl(x -> (f(x), x), _rf_findmax, domain)
+    _rf_findmax((fm, m), (fx, x)) = isless(fm, fx) ? (fx, x) : (fm, m)
+
+    Base.findmin(f, domain) = mapfoldl(x -> (f(x), x), _rf_findmin, domain)
+    _rf_findmin((fm, m), (fx, x)) = isgreater(fm, fx) ? (fx, x) : (fm, m)
+
+    Base.argmax(f, domain) = findmax(f, domain)[2]
+    Base.argmin(f, domain) = findmin(f, domain)[2]
+end
+
 include("iterators.jl")
 include("deprecated.jl")
 

test/runtests.jl

@@ -833,3 +833,36 @@ end
     @test endswith("abc", r"C"i)
     @test endswith("abc", r"Bc"i)
 end
+
+# https://github.com/JuliaLang/julia/pull/35316
+@testset "2arg" begin
+    @testset "findmin(f, domain)" begin
+        @test findmin(-, 1:10) == (-10, 10)
+        @test findmin(identity, [1, 2, 3, missing]) === (missing, missing)
+        @test findmin(identity, [1, NaN, 3, missing]) === (missing, missing)
+        @test findmin(identity, [1, missing, NaN, 3]) === (missing, missing)
+        @test findmin(identity, [1, NaN, 3]) === (NaN, NaN)
+        @test findmin(identity, [1, 3, NaN]) === (NaN, NaN)
+        @test all(findmin(cos, 0:π/2:2π) .≈ (-1.0, π))
+    end
+
+    @testset "findmax(f, domain)" begin
+        @test findmax(-, 1:10) == (-1, 1)
+        @test findmax(identity, [1, 2, 3, missing]) === (missing, missing)
+        @test findmax(identity, [1, NaN, 3, missing]) === (missing, missing)
+        @test findmax(identity, [1, missing, NaN, 3]) === (missing, missing)
+        @test findmax(identity, [1, NaN, 3]) === (NaN, NaN)
+        @test findmax(identity, [1, 3, NaN]) === (NaN, NaN)
+        @test findmax(cos, 0:π/2:2π) == (1.0, 0.0)
+    end
+
+    @testset "argmin(f, domain)" begin
+        @test argmin(-, 1:10) == 10
+        @test argmin(sum, Iterators.product(1:5, 1:5)) == (1, 1)
+    end
+
+    @testset "argmax(f, domain)" begin
+        @test argmax(-, 1:10) == 1
+        @test argmax(sum, Iterators.product(1:5, 1:5)) == (5, 5)
+    end
+end