base cmp for floats on isless instead of throwing errors

part of #5290

Author: JeffBezanson

base/float.jl

@@ -460,22 +460,6 @@ for op in (:<, :<=, :isless)
     @eval ($op)(a::Float16, b::Float16) = ($op)(Float32(a), Float32(b))
 end
 
-function cmp(x::AbstractFloat, y::AbstractFloat)
-    isnan(x) && throw(DomainError(x, "`x` cannot be NaN."))
-    isnan(y) && throw(DomainError(y, "`y` cannot be NaN."))
-    ifelse(x<y, -1, ifelse(x>y, 1, 0))
-end
-
-function cmp(x::Real, y::AbstractFloat)
-    isnan(y) && throw(DomainError(y, "`y` cannot be NaN."))
-    ifelse(x<y, -1, ifelse(x>y, 1, 0))
-end
-
-function cmp(x::AbstractFloat, y::Real)
-    isnan(x) && throw(DomainError(x, "`x` cannot be NaN."))
-    ifelse(x<y, -1, ifelse(x>y, 1, 0))
-end
-
 # Exact Float (Tf) vs Integer (Ti) comparisons
 # Assumes:
 # - typemax(Ti) == 2^n-1

base/gmp.jl

@@ -492,7 +492,7 @@ cmp(x::BigInt, y::CulongMax) = MPZ.cmp_ui(x, y)
 cmp(x::BigInt, y::Integer) = cmp(x, big(y))
 cmp(x::Integer, y::BigInt) = -cmp(y, x)
 
-cmp(x::BigInt, y::CdoubleMax) = isnan(y) ? throw(DomainError(y, "`y` cannot be NaN.")) : MPZ.cmp_d(x, y)
+cmp(x::BigInt, y::CdoubleMax) = isnan(y) ? -1 : MPZ.cmp_d(x, y)
 cmp(x::CdoubleMax, y::BigInt) = -cmp(y, x)
 
 isqrt(x::BigInt) = MPZ.sqrt(x)

base/mpfr.jl

@@ -676,23 +676,23 @@ end
 >(x::BigFloat, y::BigFloat) = ccall((:mpfr_greater_p, :libmpfr), Int32, (Ref{BigFloat}, Ref{BigFloat}), x, y) != 0
 
 function cmp(x::BigFloat, y::BigInt)
-    isnan(x) && throw(DomainError(x, "`x` cannot be NaN."))
+    isnan(x) && return 1
     ccall((:mpfr_cmp_z, :libmpfr), Int32, (Ref{BigFloat}, Ref{BigInt}), x, y)
 end
 function cmp(x::BigFloat, y::ClongMax)
-    isnan(x) && throw(DomainError(x, "`x` cannot be NaN."))
+    isnan(x) && return 1
     ccall((:mpfr_cmp_si, :libmpfr), Int32, (Ref{BigFloat}, Clong), x, y)
 end
 function cmp(x::BigFloat, y::CulongMax)
-    isnan(x) && throw(DomainError(x, "`x` cannot be NaN."))
+    isnan(x) && return 1
     ccall((:mpfr_cmp_ui, :libmpfr), Int32, (Ref{BigFloat}, Culong), x, y)
 end
 cmp(x::BigFloat, y::Integer) = cmp(x,big(y))
 cmp(x::Integer, y::BigFloat) = -cmp(y,x)
 
 function cmp(x::BigFloat, y::CdoubleMax)
-    isnan(x) && throw(DomainError(x, "`x` cannot be NaN."))
-    isnan(y) && throw(DomainError(y, "`y` cannot be NaN."))
+    isnan(x) && return isnan(y) ? 0 : 1
+    isnan(y) && return -1
     ccall((:mpfr_cmp_d, :libmpfr), Int32, (Ref{BigFloat}, Cdouble), x, y)
 end
 cmp(x::CdoubleMax, y::BigFloat) = -cmp(y,x)

base/rational.jl

@@ -285,8 +285,12 @@ end
 for rel in (:<,:<=,:cmp)
     for (Tx,Ty) in ((Rational,AbstractFloat), (AbstractFloat,Rational))
         @eval function ($rel)(x::$Tx, y::$Ty)
-            if isnan(x) || isnan(y)
-                $(rel == :cmp ? :(throw(DomainError((x,y), "Inputs cannot be NaN."))) :
+            if isnan(x)
+                $(rel == :cmp ? :(return isnan(y) ? 0 : 1) :
+                                :(return false))
+            end
+            if isnan(y)
+                $(rel == :cmp ? :(return -1) :
                                 :(return false))
             end
 

test/mpfr.jl

@@ -492,11 +492,11 @@ end
     @test isless(big(1.0), big(NaN))
 
     # cmp
-    @test cmp(big(-0.0), big(0.0)) == 0
-    @test cmp(big(0.0), big(-0.0)) == 0
-    @test_throws DomainError cmp(big(1.0), big(NaN))
-    @test_throws DomainError cmp(big(NaN), big(NaN))
-    @test_throws DomainError cmp(big(NaN), big(1.0))
+    @test cmp(big(-0.0), big(0.0)) == -1
+    @test cmp(big(0.0), big(-0.0)) == 1
+    @test cmp(big(1.0), big(NaN)) == -1
+    @test cmp(big(NaN), big(NaN)) == 0
+    @test cmp(big(NaN), big(1.0)) == 1
 end
 @testset "signbit" begin
     @test signbit(BigFloat(-1.0)) == 1