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From: jrbd@craycos.com (James Davies)
Newsgroups: comp.lang.fortran
Subject: Re: MAX function, but carry sign
Message-ID: <1991Apr12.151728.12916@craycos.com>
Date: 12 Apr 91 15:17:28 GMT
References: <282@venice.water.ca.gov>
Organization: Cray Computer Corporation
Lines: 19

In article <282@venice.water.ca.gov> rfinch@caldwr.water.ca.gov (Ralph Finch) writes:
>
>I wish to use the max function on absolute values, but carry the sign
>of the original values. That is:
>
>a=max(abs(a1),abs(a2)) ! but a has sign of either a1 or a2
>
>I'm doing this with an IF statement now but wonder if there isn't some
>combination of max and sign that will give the same result without an
>IF statement.

If you want the result to carry the sign of the maximum value 
(which is the most likely case), then you could use the sign of the sum
of the two, i.e.

	a = sign(max(abs(a1),abs(a2)), a1+a2)

This will give you the positive value if they are the same, but the sign
of the larger absolute value if they are different.