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Re: Need Help Displaying of Infix to postfix conversion

From Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups comp.lang.c
Subject Re: Need Help Displaying of Infix to postfix conversion
Date 2016-08-22 00:13 +0100
Organization A noiseless patient Spider
Message-ID <8760qtvhq6.fsf@bsb.me.uk> (permalink)
References <f3b33761-dc0c-4902-b8ce-e50f2c3430c9@googlegroups.com> <rmjjrbp57ba3ecuiv430vtirnq5drjelmd@4ax.com> <npdalf$ulu$1@dont-email.me>

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BartC <bc@freeuk.com> writes:

> On 21/08/2016 17:42, Barry Schwarz wrote:
>> On Sun, 21 Aug 2016 02:47:19 -0700 (PDT), Own IT
>
>>>        while(priority(stack[top]) >= priority(*e))
>
>> It will attempt to evaluate stack[-1] which will cause undefined
>> behavior.
>
> I had to change that line to:
>
>         while(priority(top>=0 && stack[top]) >= priority(*e))

That looks like a typo.  There are several places where stack access
needs a check for correctness.  This is one of them and you do that with

  while(top >= 0 && priority(stack[top]) >= priority(*e))

I'd write a tiny "empty()" function and a "top()" function too just to
keep all the stack stuff in one place.

> to fix the gcc problem I was seeing.

I don't think it's a gcc problem -- it's a code problem.

-- 
Ben.

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Thread

Need Help Displaying of Infix to postfix conversion Own IT <beltondavid1@gmail.com> - 2016-08-21 02:47 -0700
  Re: Need Help Displaying of Infix to postfix conversion BartC <bc@freeuk.com> - 2016-08-21 11:17 +0100
    Re: Need Help Displaying of Infix to postfix conversion Keith Thompson <kst-u@mib.org> - 2016-08-21 15:43 -0700
      Re: Need Help Displaying of Infix to postfix conversion BartC <bc@freeuk.com> - 2016-08-21 22:17 +0100
        Re: Need Help Displaying of Infix to postfix conversion Keith Thompson <kst-u@mib.org> - 2016-08-21 18:17 -0700
  Re: Need Help Displaying of Infix to postfix conversion Barry Schwarz <schwarzb@dqel.com> - 2016-08-21 09:42 -0700
    Re: Need Help Displaying of Infix to postfix conversion Siri Cruise <chine.bleu@yahoo.com> - 2016-08-21 11:24 -0700
    Re: Need Help Displaying of Infix to postfix conversion BartC <bc@freeuk.com> - 2016-08-21 23:40 +0100
      Re: Need Help Displaying of Infix to postfix conversion Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-22 00:13 +0100
        Re: Need Help Displaying of Infix to postfix conversion BartC <bc@freeuk.com> - 2016-08-22 01:31 +0100
          Re: Need Help Displaying of Infix to postfix conversion David Kleinecke <dkleinecke@gmail.com> - 2016-08-21 20:13 -0700
    Re: Need Help Displaying of Infix to postfix conversion supercat@casperkitty.com - 2016-08-22 09:44 -0700
      Re: Need Help Displaying of Infix to postfix conversion Barry Schwarz <schwarzb@dqel.com> - 2016-08-22 10:18 -0700
        Re: Need Help Displaying of Infix to postfix conversion supercat@casperkitty.com - 2016-08-22 10:27 -0700
          Re: Need Help Displaying of Infix to postfix conversion "Osmium" <r124c4u102@comcast.net> - 2016-08-22 16:05 -0500
        Usenet in general and CLC in particular (Was: Need Help something or other...) gazelle@shell.xmission.com (Kenny McCormack) - 2016-08-25 11:48 +0000

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