Make lcm(Rational[]) throw.

JuliaLang · Dec 31, 2024 · 2ef55d8 · 2ef55d8
1 parent 79d3f77
commit 2ef55d8
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Showing 2 changed files with 5 additions and 2 deletions.
diff --git a/base/intfuncs.jl b/base/intfuncs.jl
@@ -153,7 +153,10 @@ gcd(abc::AbstractArray{<:Real}) = reduce(gcd, abc; init=zero(eltype(abc)))
 function lcm(abc::AbstractArray{<:Real})
     # Using reduce with init=one(eltype(abc)) is buggy for Rationals.
     l = length(abc)
-    l == 0 && return one(eltype(abc))
+    if l == 0
+        eltype(abc) <: Integer && return one(eltype(abc))
+        throw(ArgumentError("lcm has no identity over $(eltype(abc))"))
+    end
     l == 1 && return abs(only(abc))
     return reduce(lcm, abc)
 end

diff --git a/test/intfuncs.jl b/test/intfuncs.jl
@@ -197,7 +197,7 @@ end
     @test gcd(Int[]) === 0
     @test lcm(Int[]) === 1
     @test gcd(Rational{Int}[]) === 0//1
-    @test lcm(Rational{Int}[]) === 1//1
+    @test_throws ArgumentError("lcm has no identity on Rational{Int}") lcm(Rational{Int}[])
 end
 
 ⟷(a::Tuple{T, T, T}, b::Tuple{T, T, T}) where T <: Union{Int8, UInt8, Int16, UInt16, Int32, UInt32, Int64, UInt64, Int128, UInt128} = a === b