From 197aca97f1b64193e2d678e7e416266a77402e9b Mon Sep 17 00:00:00 2001
From: Sacha Verweij <sacha@stanford.edu>
Date: Mon, 9 Jan 2017 10:57:21 -0800
Subject: [PATCH] Deprecate isimag.

---
 base/complex.jl           | 6 ------
 base/deprecated.jl        | 3 +++
 base/exports.jl           | 1 -
 doc/src/stdlib/numbers.md | 1 -
 test/complex.jl           | 6 +++---
 5 files changed, 6 insertions(+), 11 deletions(-)

diff --git a/base/complex.jl b/base/complex.jl
index 16cc55e87b342..9838f216060dd 100644
--- a/base/complex.jl
+++ b/base/complex.jl
@@ -90,12 +90,6 @@ false
 """
 isreal(x::Real) = true
 isreal(z::Complex) = iszero(imag(z))
-"""
-    isimag(z) -> Bool
-
-Test whether `z` is purely imaginary, i.e. has a real part equal to 0.
-"""
-isimag(z::Number) = iszero(real(z))
 isinteger(z::Complex) = isreal(z) & isinteger(real(z))
 isfinite(z::Complex) = isfinite(real(z)) & isfinite(imag(z))
 isnan(z::Complex) = isnan(real(z)) | isnan(imag(z))
diff --git a/base/deprecated.jl b/base/deprecated.jl
index 773ec6ae95bfb..096fb21b2523c 100644
--- a/base/deprecated.jl
+++ b/base/deprecated.jl
@@ -1278,6 +1278,9 @@ eval(SparseArrays, :(broadcast_zpreserving!(f, C::SparseMatrixCSC, A::Union{Arra
 @deprecate getindex(t::Tuple, r::AbstractArray)       getindex(t, vec(r))
 @deprecate getindex(t::Tuple, b::AbstractArray{Bool}) getindex(t, vec(b))
 
+# Deprecate isimag (#19947).
+@deprecate isimag(z::Number) iszero(real(z))
+
 @deprecate airy(z::Number) airyai(z)
 @deprecate airyx(z::Number) airyaix(z)
 @deprecate airyprime(z::Number) airyaiprime(z)
diff --git a/base/exports.jl b/base/exports.jl
index 0020e1120482e..5321c087627fb 100644
--- a/base/exports.jl
+++ b/base/exports.jl
@@ -358,7 +358,6 @@ export
     ispow2,
     isqrt,
     isreal,
-    isimag,
     issubnormal,
     iszero,
     lcm,
diff --git a/doc/src/stdlib/numbers.md b/doc/src/stdlib/numbers.md
index 8a6508d0ae326..ffce0a45ac16f 100644
--- a/doc/src/stdlib/numbers.md
+++ b/doc/src/stdlib/numbers.md
@@ -72,7 +72,6 @@ Base.nextfloat
 Base.prevfloat
 Base.isinteger
 Base.isreal
-Base.isimag
 Core.Float32
 Core.Float64
 Base.GMP.BigInt
diff --git a/test/complex.jl b/test/complex.jl
index bb9aa2d0e7a02..8bd7435457e74 100644
--- a/test/complex.jl
+++ b/test/complex.jl
@@ -147,9 +147,9 @@ end
     end
 end
 
-@testset "isimag and isinf" begin
-    @test isimag(complex(0.0,1.0))
-    @test !isimag(complex(1.0,1.0))
+@testset "isinf" begin
+    @test iszero(real(complex(0.0,1.0))) # isimag deprecated
+    @test !iszero(real(complex(1.0,1.0))) # isimag deprecated
     @test isinf(complex(Inf,0))
     @test isinf(complex(-Inf,0))
     @test isinf(complex(0,Inf))