NetNews Usenet Archive 1992 #30/NN_1992_30.iso/spool/comp/lang/c/18279

Internet Message Format | 1992-12-12 | 2.9 KB

Path: sparky!uunet!crdgw1!rdsunx.crd.ge.com!bart!volpe
From: [e-mail] (Christopher R Volpe)
Newsgroups: comp.lang.c
Subject: Re: HELP with C syntax checking programm
Keywords: c help braces { } fix syntax
Message-ID: <[e-mail]>
Date: 13 Dec 92 01:20:16 GMT
References: <[e-mail]>
Sender: volpe@bart (Christopher R Volpe)
Reply-To: [e-mail]
Distribution: all
Organization: GE Corporate Research & Development
Lines: 81
Nntp-Posting-Host: bart.crd.ge.com

In article <[e-mail]>, [e-mail] (j. hurwitz) writes:
|> Okay, I'm new to C so you'll have to forgive my lame question. Anyhoot,
|> I'm trying to write a program that will check for balanced braces in my
|> C source code. I hve no problem when I do this:
|>
|> =========================== Begin Hack =============================
|> //programm to read a C source file and verify # of left to right braces
|> #include <stdio.h>
|>
|> int main(int argc, char *argv[])
|> {
|>    FILE *fptr;
|>    int l=0, r=0;
|>    char ch;

Here is a problem, though it's not what's causing your problems. "Ch" must
be declared an int, not a char, because that is what getc returns. The reason
is that a char cannot hold all the characters AND a unique EOF value. So,
depending on how your system implements chars (are they signed or unsigned?),
either a valid character will be mistaken for EOF, or EOF will be mistaken
for a valid char.

|>
|>    fptr  = fopen("brachek2.c","r");
|>
|>    while ((ch =getc(fptr)) !=EOF)      //gets chars
|>    {
|>    if(ch=='{') l++;
|>    if(ch=='}') r++;
|>    }
|>    if (l != r)
|>   printf("\nBraces do not match\n");
|>    else printf("\nBraces match !!!\n");
|>    fclose(fptr);
|>    return(0);
|> }
|> =========================== End Hack ===============================
|>
|> But, when I try this:
|>
|> ============================== Begin Hack ==========================
|>
|> //programm to read a C source file and verify # of left to right braces
|> #include <stdio.h>
|>
|> int main(int argc, char *argv[])
|> {
|>    FILE *fptr;
|>    int l=0, r=0;
|>    char ch;
|>
|>    fptr  = fopen("brachek3.c","r");
|>
|>    while ((ch =getc(fptr)) !=EOF)      //gets chars
|>    {
|>    switch (ch)
|>      {
|>      case '{':  l++;

Here's your real problem. You need a "break" separating the cases, otherwise
execution will flow from one case right into the next.

|>      case '}':  r++;
|>      }
|>    }
|>    printf("\nl= %d r= %d", l, r);
|>    if (l != r)
|>    printf("\nBraces do not match\n");
|>    else printf("\nBrace match !!!\n");
|>    fclose(fptr);
|> }
|> ================================ End Hack ==========================
|> I get an uneven number of braces at the end. I can't figure out what
|> I am doing wrong. I'm sure it is a minor oversight on my part. Any help
|> would be greatly appreciated.

--
==================
Chris Volpe
G.E. Corporate R&D
[e-mail]