complete curried comparisons (#30915)

* add !=(x) <=(x) >=(x) <(x) >(x)
* add tests for curried comparisons

base/operators.jl

@@ -927,6 +927,56 @@ used to implement specialized methods.
 """
 ==(x) = Fix2(==, x)
 
+"""
+ !=(x)
+
+Create a function that compares its argument to `x` using [`!=`](@ref), i.e.
+a function equivalent to `y -> y != x`.
+The returned function is of type `Base.Fix2{typeof(!=)}`, which can be
+used to implement specialized methods.
+"""
+!=(x) = Fix2(!=, x)
+
+"""
+ >=(x)
+
+Create a function that compares its argument to `x` using [`>=`](@ref), i.e.
+a function equivalent to `y -> y >= x`.
+The returned function is of type `Base.Fix2{typeof(>=)}`, which can be
+used to implement specialized methods.
+"""
+>=(x) = Fix2(>=, x)
+
+"""
+ <=(x)
+
+Create a function that compares its argument to `x` using [`<=`](@ref), i.e.
+a function equivalent to `y -> y <= x`.
+The returned function is of type `Base.Fix2{typeof(<=)}`, which can be
+used to implement specialized methods.
+"""
+<=(x) = Fix2(<=, x)
+
+"""
+ >(x)
+
+Create a function that compares its argument to `x` using [`>`](@ref), i.e.
+a function equivalent to `y -> y > x`.
+The returned function is of type `Base.Fix2{typeof(>)}`, which can be
+used to implement specialized methods.
+"""
+>(x) = Fix2(>, x)
+
+"""
+ <(x)
+
+Create a function that compares its argument to `x` using [`<`](@ref), i.e.
+a function equivalent to `y -> y < x`.
+The returned function is of type `Base.Fix2{typeof(<)}`, which can be
+used to implement specialized methods.
+"""
+<(x) = Fix2(<, x)
+
 """
  splat(f)
 

test/operators.jl

@@ -196,3 +196,20 @@ end
  @test fx(y) == x / y
  @test fy(x) == x / y
 end
+
+
+@testset "curried comparisons" begin
+ eql5 = (==)(5)
+ neq5 = (!=)(5)
+ gte5 = (>=)(5)
+ lte5 = (<=)(5)
+ gt5 = (>)(5)
+ lt5 = (<)(5)
+
+ @test eql5(5) && !eql5(0)
+ @test neq5(6) && !neq5(5)
+ @test gte5(5) && gte5(6)
+ @test lte5(5) && lte5(4)
+ @test gt5(6) && !gt5(5)
+ @test lt5(4) && !lt5(5)
+end