Challenges

# Multiply complex numbers.

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Multiply complex numbers. 2 space-seperated ones will be input, as follows: (update: you can replace i with j or some other symbol if needed)

a+bi -a+bi a-bi -a-bi

where a and b are integers written in base 10.

You are expected to output in the same format.

For those unfamiliar: $i$ is the imaginary constant, the value of $\sqrt{-1}$, and a complex number is the sum of a real number and an imaginary number.

Shortest code following the rules wins.

EDIT: test cases:

• 3+4i 4-5i -> 32+1i
• -4+9i 2-2i -> 10+26i
• -4+9i 2+2i -> -26+10i
• -3+0i 10+0i -> -30+0i
• 0+1i 0+1i -> -1+0i
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First test case is incorrect (3 comments)

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# Python 3, 98 bytes

print(str(eval("("+input().replace(" ",")*(").replace("i","j")+")")).strip("()").replace("j","i"))


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Since the input format is restrictive, I may as well just spam replace and abuse eval.

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# JavaScript (Node.js), 9996 69 bytes

s=>([a,b,c,d]=s.match(/-?\d+/g),a*c-b*d+(a=a*d+b*c,a<0?'':'+')+a+'i')


Try it online!

This regex is probably the best way to get the numbers.

Also, for some reason, JavaScript math works with strings of numbers, so that's convenient.

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# Ruby, 35 bytes

->a{a.split.map{eval _1}.reduce :*}


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Right tool for the job, I suppose.

uses ruby 2.7+ features, so tio link will look different.

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