The package Interfaces.C has several subroutines that deal with null-
terminated strings. From http://www.adahome.com/rm95/rm9x-B-03.html:
function Is_Nul_Terminated (Item : in char_array) return Boolean;
The result of Is_Nul_Terminated is True if Item contains nul, and is
False otherwise.
There are a number of functions and procedures to convert stuff and
they all look something like this. (Ada allows overloads so they go
by the same name).
function To_C
(Item : in String;
Append_Nul : in Boolean := True)
return char_array;
function To_Ada
(Item : in char_array;
Trim_Nul : in Boolean := True)
return String;
Note also that Ada arguments are optional after the first one as long
as they have a default value as determined by the := within the
formal argument list, so To_C(In_String) is the same as To_C
(In_String, True). Ada itself has extensive string processing built
in and will initially drive one crazy with its three different string
types. Werner's solution of appending the null character with & Nul
does the same thing.
I'll look into this further as soon as I finish some minutia related
to my weird Ada installation and getting the ctest stuff to work.
Jerry
On Mar 13, 2007, at 3:34 AM, Werner Smekal wrote:
> Hi Alan,
>> However, that was because I replaced
>> - plbox("bc", 0.0, 0, "bc", 0.0, 0);
>> + Box_Around_Viewport(TUB("bc"), 0.0, 0, TUB("bc"), 0.0, 0);
>>
>> If I use plbox rather than Box_Around_Viewport, then the result has
>> extraneous tick marks. I don't understand the cause of this
>> problem. The
>> same example has a call to plptex with another character array,
>> and that
>> works without problems. I have also carefully compared how plptex
>> and plbox
>> are set up in plplotthin.ads, and I cannot spot anything. I also
>> tried the
>> TUB("bc") in the argument list for plbox, but the compiler
>> complained about
>> something being inconsistent before erroring out so I dropped it.
> I found the solution to this problem. Have a look into example x12.
> The
> thin bindings of plplot need as strings char_array , but in Ada a '\0'
> is not automatically added. You need to do this on you own. You
> need the
> "Interfaces.C" library/module/whatever and than add "& Nul" to the
> strings so that they have the correct ending. Maybe Jerry can tell you
> how exactly this is supposed to work, or give a better/nicer
> solution to
> this problem.
>
> Regards,
> Werner
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