Merge pull request #107 from ikaliuzh/patch-1

Update factorials.jl

Author: logankilpatrick

src/factorials.jl

@@ -71,7 +71,8 @@ function partialderangement(n::Integer, k::Integer)
 end
 
 # Hyperfactorial
-hyperfactorial(n::Integer) = prod(i->i^i, BigInt(2):n)
+hyperfactorial(n::Integer) = n==0 ? BigInt(1) : prod(i->i^i, BigInt(1):n)
+
 
 function multifactorial(n::Integer, m::Integer)
     if n < 0

test/factorials.jl

@@ -22,6 +22,9 @@
 
 # hyperfactorial
 @test hyperfactorial(8) == parse(BigInt,"55696437941726556979200000")
+@test hyperfactorial(0) == parse(BigInt,"1")
+@test hyperfactorial(1) == parse(BigInt,"1")
+@test hyperfactorial(2) == parse(BigInt,"4")
 
 # multifactorial
 @test multifactorial(40,2) == doublefactorial(40)