Re: [ gnuplot-Patches-992149 ] String variables revisited

[Ethan A M. <merritt@u.washington.edu>]

On Wednesday 21 July 2004 12:33 am, Volker Dobler wrote:
> There are two functions: quote_str and m_quote_capture.
> Using quote_str you will have to do memory allocation yourself,
> whereas m_quote_capture will do allocation for you if I remember
> correctly.  My old patch replaced (hopfully) all the invocations
> of quote_str with m_quote_capture and did substitution there.

You guys may yet convince me. I think it may be even cleaner than
you describe, because the expression parsing code can now handle
string constants as well as string-valued functions.  So many of the
instances of isstring() + m_quote_capture() can be replaced by
const_express(&a).  Better yet, in many places this is what the code
was going to try next anyhow.  So the test for string constants
as a special case just goes away. 

Example (taken from the "print" command):

#ifndef GP_STRING_VARS       /* This is the version 4.0 code */
        if (isstring(c_token)) {
            s = NULL;
            m_quote_capture(&s, c_token, c_token);
            fputs(s, print_out);
            need_space = 0;
            free(s);
            ++c_token;
        } else {
            (void) const_express(&a);
            if (need_space)
                putc(' ', print_out);
            need_space = 1;
            disp_value(print_out, &a);
        }
#else    /* This is the code after adding string variables */
        (void) const_express(&a);
        disp_value(print_out, &a);
        if (a.type == STRING)
            free(a.v.string_val);
        else
            putc(' ', print_out);
#endif


Yes, I know that this code fragment does not exactly duplicate
the whitespace layout of the old behaviour.
I also see that I must work on when, if ever, to print
quote marks when showing the value of string variables.  

The only thing I am stuck on at the moment is trying to
automatically free the dynamically-allocated string created
by evaluation of const_express(&a).  It is annoying to test for
it everywhere, though I suppose it's no worse than having to do
the same thing after m_quote_capture in the current code.


-- 
Ethan A Merritt
Department of Biochemistry & Biomolecular Structure Center
University of Washington, Seattle