CODEWITHSUNDEEP
julia
Andreas Dibiasi
Andreas Dibiasi

Reputation: 271

Fortran's SIGN function in Julia

Exists there a function in Julia that is equivalent to the SIGN(A,B) function in Fortran?

SIGN(A,B) in Fortran returns the value of A with the sign of B. If B > 0 then the result is ABS(A), else it is -ABS(A). For instance, SIGN(10,-1) would give you -10.

Upvotes: 1

Views: 233

Answers (2)

Bogumił Kamiński
Bogumił Kamiński

Reputation: 69949

You have copysign function that does what you want.

The only distinction from what you have specified is that copysign(1.0, 0.0) return 1.0 and you specified it to be -1.0 (by saying B>0), but I guess you want this to evaluate to 1.0 like copysign behaves. Right?. Note that copysign(1.0, -0.0) is -1.0.

Upvotes: 4

Colin T Bowers
Colin T Bowers

Reputation: 18580

EDIT: Check Bogumil's answer. Turns out there is a function in Base that does this.

I don't think there is a function in Base that does this. However, adding a new method to sign is an easy solution:

Base.sign(a, b) = abs(a)*sign(b)

You can use methods(sign) to check that your new method won't clash with any existing methods. In this case, it definitely won't since all existing methods only have a single input.

The behaviour of the new method will also be consistent with all existing input types, eg sign(missing, -1) will return missing, and sign(true, false) will return false.

Alternatively, you could come up with your own new function name.

Upvotes: 2

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