Math: Get Just the Sign

[tentus]

You know how math.abs returns a variable, sans its sign? Does anyone there a neat trick for doing the opposite, short of using the below:

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function sign(x)
  if x < 0 then
    return -1
  end
  return 1
end

(And before anyone suggests it, we do not want 0.)

[bartbes]

I only know the easy (yet probably inefficient) x/math.abs(x). (That has 0, though..)
Of course I don't know your gripe with the if, but you could shorten it to x < 0 and -1 or 1.

[molul]

You can define it as a math function, like this:

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function math.sign(x)
	return (x >= 0) and 1 or -1
end

This counts 0 as positive. If you want to identify zeros, do this:

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function math.sign(x)
	return (x > 0) and 1 or (x < 0) and -1 or 0
end

[Le Codex]

If you want to test the sign, you can just use math.abs(var) == var to test if it's positive

Example:

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var = 1
negvar = -1

if math.abs(var) == var then true end
if math.abs(negvar) == negvar then false end
if math.abs(negvar) == -negvar then true end