Re: Glib::ustring conversion

[Bob Caryl <bob fis-cal com>]

Arthur wrote:

> Hi there.
>
> I'm building a simple calculator with Glade(mm) and I would like to 
> know if it is possible to convert Glib::ustring to double and then 
> double to Glib::ustring.
> I need this because the calculator has an entrytext widget and when I 
> press the numbers and signs (plus, minus, multiply, divide, left 
> parenthesis and right parenthesis) a string is shown at this entry 
> text: "1254 + 13241 - (13241 * 1341)". When the equal button (=) is 
> pressed I want to pass this string as a double and make C++ to solve 
> this mathematic expression for me and return the result, so I can set 
> it as the entry text string again.
>
> If anyone could help me, I would appreciate.
>
> Regards,
>
> Arthur
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I don't know of any library function in the standard C library that 
would do what you describe.  However, glib has a pair of routines:  
g_ascii_strtod() and g_ascii_dtostr() (see docs 
<http://developer.gnome.org/doc/API/2.0/glib/glib-String-Utility-Functions.html#g-ascii-strtod> 
for syntax).  They will convert ascii strings to doubles, and doubles to 
ascii strings...

Unfortunately, you cannot pass the entire string you'll get back from 
your from your Gtk::Entry widget (Glib::ustring::c_str())  to 
g_ascii_strtod and expect the answer to your calculation.  You will have 
to parse your string and use g_ascii_strtod to convert all the number 
strings and perform the calculations yourself.  Depending on the level 
of the calculation and how deeply nested your expression is, that would 
not be a trivial undertaking.

Bob