[m-dev.] complex numbers

[Fergus Henderson]

Andrew Bromage, you wrote:
> Fergus Henderson wrote:
> 
> > +	% norm (square of absolute value)
> > +	% XXX is `norm' the right terminology?
> > +:- func norm(complex) = float.
> 
> Uhm... no, it isn't.  But I don't know what it is.  Perhaps sqr_abs
> is a better name?

I called it `abs2'.

> I think it might be useful (for completeness) to provide the following
> functions:
> 
> <<
> :- func conjugate(complex) = complex.
> :- mode conjugate(in) = out is det.
> 
> conjugate(cmplx(X, Y)) = cmplx(X, -Y).
> 
> :- func cis(float) = complex.
> :- mode cis(in) = out is det.
> 
> 	% cis(Theta) is a shorthand for polar_to_complex(1.0, Theta)
> cis(Theta) = cmplx(cos(Theta), sin(Theta)).
> >>

Done, except I called it `conj' rather than `conjugate'.
(For consistency with the other short names used in this module:
arg[ument], imag[inary_part] real[_part], and sqrt [instead of square_root].
Mathematicians seem to prefer short names. :-)

-- 
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