Re: Token Parser

CBFalconer wrote:
"T.M. Sommers" wrote:
CBFalconer wrote: 
"T.M. Sommers" wrote:

Use this instead:

          while ( (c = getchar()) != EOF && isdigit(c) )  {

This was an error in the code I posted earlier.  You don't want
to isdigit(EOF).


This is an error.  He wants to find the non-digit operators also.
There is no problem passing EOF to isdigit, it will reply 'no'.


You are quite right.  I was under the impression that the
argument had to be an unsigned char, but the standard also allows
EOF.


The error part was that you changed the logic so that it could no
longer return the various operators, skipblanks, etc.  The other is
unnecessary, rather than an error.

I cut and pasted from my own code, which used a different variable for the input character ('c' vice 'next_token'), which was an error, but other than that I don't see any error in the above line (except that one should perhaps guarantee that c can be cast to unsigned char). The loop controlled by the while is over digits after the first, and will stop when and only when c is not a digit. The only thing the EOF test changes is that isdigit() will not be called for EOF, which, as you pointed out, is unnecessary.

--
Thomas M. Sommers -- tms@xxxxxx -- AB2SB

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