define round/trunc/ceil/floor to Bool (#25085)

Author: simonbyrne

base/float.jl

@@ -358,6 +358,12 @@ floor(::Type{T}, x::AbstractFloat) where {T<:Integer} = trunc(T,round(x, RoundDo
 ceil(::Type{T}, x::AbstractFloat) where {T<:Integer} = trunc(T,round(x, RoundUp))
 round(::Type{T}, x::AbstractFloat) where {T<:Integer} = trunc(T,round(x, RoundNearest))
 
+# Bool
+trunc(::Type{Bool}, x::AbstractFloat) = (-1 < x < 2) ? 1 <= x : throw(InexactError(:trunc, Bool, x))
+floor(::Type{Bool}, x::AbstractFloat) = (0 <= x < 2) ? 1 <= x : throw(InexactError(:floor, Bool, x))
+ceil(::Type{Bool}, x::AbstractFloat)  = (-1 < x <= 1) ? 0 < x : throw(InexactError(:ceil, Bool, x))
+round(::Type{Bool}, x::AbstractFloat) = (-0.5 <= x < 1.5) ? 0.5 < x : throw(InexactError(:round, Bool, x))
+
 round(x::IEEEFloat, r::RoundingMode{:ToZero})  = trunc_llvm(x)
 round(x::IEEEFloat, r::RoundingMode{:Down})    = floor_llvm(x)
 round(x::IEEEFloat, r::RoundingMode{:Up})      = ceil_llvm(x)

test/numbers.jl

@@ -2813,3 +2813,45 @@ end
     @test_throws MethodError fld(a, b)
     @test_throws MethodError cld(a, b)
 end
+
+@testset "Bool rounding (#25074)" begin
+    @testset "round Bool" begin
+        @test_throws InexactError round(Bool, -4.1)
+        @test_throws InexactError round(Bool, 1.5)
+        @test true == round(Bool, 1.0)
+        @test false == round(Bool, 0.0)
+        @test true == round(Bool, 0.6)
+        @test false == round(Bool, 0.4)
+        @test false == round(Bool, 0.5)
+        @test false == round(Bool, -0.5)
+    end
+
+    @testset "trunc Bool" begin
+        @test_throws InexactError trunc(Bool, -4.1)
+        @test_throws InexactError trunc(Bool, 2.5)
+        @test true == trunc(Bool, 1.0)
+        @test false == trunc(Bool, 0.0)
+        @test false == trunc(Bool, 0.6)
+        @test false == trunc(Bool, 0.4)
+        @test true == trunc(Bool, 1.8)
+        @test false == trunc(Bool, -0.5)
+    end
+
+    @testset "floor Bool" begin
+        @test_throws InexactError floor(Bool, -0.1)
+        @test_throws InexactError floor(Bool, 2.5)
+        @test true == floor(Bool, 1.0)
+        @test false == floor(Bool, 0.0)
+        @test false == floor(Bool, 0.6)
+        @test true == floor(Bool, 1.8)
+    end
+
+    @testset "ceil Bool" begin
+        @test_throws InexactError ceil(Bool, -1.4)
+        @test_throws InexactError ceil(Bool, 1.5)
+        @test true == ceil(Bool, 1.0)
+        @test false == ceil(Bool, 0.0)
+        @test true == ceil(Bool, 0.6)
+        @test false == ceil(Bool, -0.7)
+    end
+end