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From: draper@inmet.inmet.com
Newsgroups: comp.lang.c
Subject: Re: Trouble with curses
Message-ID: <20900013@inmet>
Date: 29 Oct 90 22:02:00 GMT
References: <173826@<1990Oct27>
Lines: 44
Nf-ID: #R:<1990Oct27:173826:inmet:20900013:000:1564
Nf-From: inmet.inmet.com!draper    Oct 29 17:02:00 1990


	I received mail today saying that I had correctly identified the
	line of code in the curses problem that was causing the problem,
	but I had missed the problem altogehter.

	These were my comments on the following line:


  	switch(tolower(getch())) {
  	/* I would watch out on the above line of code. tolower is a */
  	/* macro that might have undesriable effects should the user */
  	/* enter a character that is already in lower case. A good   */
  	/* thing to do would be check if the char was an upper case  */
  	/* using "isupper" before calling "tolower".                 */

	It was brought to my attemntion that the macro 'tolower'
	might expand out so that getch() is called twice. That
	would cause the error that was described in the posting.
	I could not beleive that I missed that. I plead guilty
	to not thinking of that, BUT I DID NOT miss it. On the
	system I am using, Sun4 , in the file ctype.h , the macro
	tolower is defined as follows:

	#define tolower(c) ((c)-'A'+'a')

	I would like to thank the indivdual who sent mail to me
	on this (sorry I mistakenly deleted your mail before
	I saved it to a file) . It is a situation that I haven't
	ran across myself.

	Moral of the story: Always make sure you know, or at least
	think you know, how your macros will expand. When in doubt
	run the code throught cpp and look at the expansions.

	- Dave


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