ntuple(f, -1) throws ArgumentError

JuliaLang · May 5, 2017 · 2c7dc16 · 2c7dc16
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diff --git a/NEWS.md b/NEWS.md
@@ -12,6 +12,9 @@ Breaking changes
 
 This section lists changes that do not have deprecation warnings.
 
+ * `ntuple(f, n::Integer)` throws `ArgumentError` if `n` is negative.
+ Previously an empty tuple was returned ([#21697]).
+
 Library improvements
 --------------------
 

diff --git a/base/tuple.jl b/base/tuple.jl
@@ -105,7 +105,8 @@ julia> ntuple(i -> 2*i, 4)
 ```
 """
 function ntuple(f::F, n::Integer) where F
- t = n <= 0 ? () :
+ (n >= 0) || throw(ArgumentError(string("tuple length should be ≥0, got ", n)))
+ t = n == 0 ? () :
  n == 1 ? (f(1),) :
  n == 2 ? (f(1), f(2)) :
  n == 3 ? (f(1), f(2), f(3)) :

diff --git a/test/tuple.jl b/test/tuple.jl
@@ -181,6 +181,8 @@ for n = 0:20
  @test t[i] == i
  end
 end
+# issue #21697
+@test_throws ArgumentError ntuple(identity, -1)
 
 # issue #19719
 @test_throws BoundsError (1,2,3)[falses(4)]