From 512339ba4b41a8f06134123a309405ea5af716de Mon Sep 17 00:00:00 2001
From: Alex Arslan <ararslan@comcast.net>
Date: Tue, 10 Jan 2017 14:05:51 -0800
Subject: [PATCH] RFC: Export iszero (#19950)

* Export and test Base.iszero
---
 NEWS.md                   |  2 ++
 base/exports.jl           |  1 +
 doc/src/stdlib/numbers.md |  1 +
 test/numbers.jl           | 16 ++++++++++++++++
 4 files changed, 20 insertions(+)

diff --git a/NEWS.md b/NEWS.md
index 81db6bd8a8609..4debf14c80e7a 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -159,6 +159,8 @@ Library improvements
   * `logging` can be used to redirect `info`, `warn`, and `error` messages
     either universally or on a per-module/function basis ([#16213]).
 
+  * New `iszero(x)` function to quickly check whether `x` is zero (or is all zeros, for an array) ([#19950]).
+
 Compiler/Runtime improvements
 -----------------------------
 
diff --git a/base/exports.jl b/base/exports.jl
index a15267a329604..0020e1120482e 100644
--- a/base/exports.jl
+++ b/base/exports.jl
@@ -360,6 +360,7 @@ export
     isreal,
     isimag,
     issubnormal,
+    iszero,
     lcm,
     ldexp,
     leading_ones,
diff --git a/doc/src/stdlib/numbers.md b/doc/src/stdlib/numbers.md
index 715a8319f9b18..8a6508d0ae326 100644
--- a/doc/src/stdlib/numbers.md
+++ b/doc/src/stdlib/numbers.md
@@ -67,6 +67,7 @@ Base.issubnormal
 Base.isfinite
 Base.isinf
 Base.isnan
+Base.iszero
 Base.nextfloat
 Base.prevfloat
 Base.isinteger
diff --git a/test/numbers.jl b/test/numbers.jl
index 75e950d2511f7..f260609b25be3 100644
--- a/test/numbers.jl
+++ b/test/numbers.jl
@@ -2864,3 +2864,19 @@ let types = (Base.BitInteger_types..., BigInt, Bool)
 end
 
 @test !isempty(complex(1,2))
+
+@testset "iszero" begin
+    # Numeric scalars
+    for T in Iterators.flatten(subtypes.([AbstractFloat, Signed, Unsigned]))
+        @test iszero(T(0))
+        @test iszero(Complex{T}(0))
+    end
+    @test iszero(BigFloat(0))
+    @test !iszero(nextfloat(BigFloat(0)))
+    @test iszero(BigInt(0))
+    @test iszero(0//1)
+
+    # Array reduction
+    @test !iszero([0, 1, 2, 3])
+    @test iszero(zeros(Int, 5))
+end