samof76
Hi I have written the following program math.ex
defmodule Math do
def mul(_, 0) do
0
end
def mul(0, _) do
0
end
def mul(a, b) when b < 0 do
sum = a + mul(a, b+1)
sum*(-1)
end
def mul(a, b) do
sum = a + mul(a, b-1)
sum
end
end
Now, when it try to the do Math.mul(4,-10) the expected answer is the -40 but it gives me 0. Also if i change the line 7 to just return sum instead of sum*(-1) I get 40.
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ityonemo
those results very much seem correct! I suggest unrolling your math carefully. Maybe do
Math.mul(4, -2)by hand.NobbZ
mul(a, -1)returns-a,mul(a, -2)returns-(a + mul(a, -1))which is-(a - a)which is-a + a, which is0.So on an even second argument you’ll always get
0and on odds you get-a.