RFC: Export iszero (#19950)

* Export and test Base.iszero

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
 -----------------------------
 

base/exports.jl

@@ -360,6 +360,7 @@ export
     isreal,
     isimag,
     issubnormal,
+    iszero,
     lcm,
     ldexp,
     leading_ones,

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

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