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From: mparisi@ripple.jpl.nasa.gov (Mark Parisi)
Newsgroups: comp.lang.fortran
Subject: Re: Checking a string for an integer
Message-ID: <1991Apr1.222449.12621@jato.jpl.nasa.gov>
Date: 1 Apr 91 22:24:49 GMT
References: <1991Apr1.104227.243@biivax.dp.beckman.com> <009467BE.E4367B40@vmsd.csd.mu.edu>
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In article <009467BE.E4367B40@vmsd.csd.mu.edu>,
8099pierzina@vmsd.csd.mu.edu (Todd Pierzina) writes:
|>    read (String, '(I3)', err=1000, iostat=iostat) i

This doesn't work quite as well as you might think.

In VMS Fortran, this will pass anything which resembles a valid 
real or integer format, including:

	"1E2"
	"D  "
	"Q  "

If you are really worried about checking for valid input, you are 
best off checking that each character in the string is between
"0" and "9".  (You will probably want to allow blanks in some 
places, this will complicate things.)

The intrinsic function INDEX is useful for performing this 
check:

	CHARACTER*(*) DIGITS
	PARAMETER (DIGITS = '0123456789')

	INTEGER I
	LOGICAL VALID
	...

	VALID = .TRUE.
	DO 10 I = 1, LEN(STR)
	   IF INDEX(DIGITS, STR(I:I) .EQ. 0) VALID = .FALSE.
10	CONTINUE

... you get the idea.

		-- Mark Parisi (mparisi@ripple.jpl.nasa.gov)