• "Mars" <- -.-> Jan 24 2012
• Mantis <mail.mantis.88 gmail.com> Jan 24 2012
• "Jonathan M Davis" <jmdavisProg gmx.com> Jan 24 2012
• mta`chrono <chrono mta-international.net> Jan 24 2012
• "Mars" <- -.-> Jan 25 2012

"Mars" <- -.-> writes:

Hello everybody.
I have to convert a char* (from a C function) to long. At the 
moment I'm using
long foo = to!long( to!string(bar) );


to go? Or is there something better?

Mars

Mantis <mail.mantis.88 gmail.com> writes:

24.01.2012 22:48, Mars пишет:
 Hello everybody.
 I have to convert a char* (from a C function) to long. At the moment 
 I'm using
 long foo = to!long( to!string(bar) );


 Or is there something better?

 Mars



char[] c = "123\0".dup;
auto l = parse!long(c);
writeln( l );

"Jonathan M Davis" <jmdavisProg gmx.com> writes:

On Tuesday, January 24, 2012 23:02:18 Mantis wrote:
 24.01.2012 22:48, Mars пишет:
 Hello everybody.
 I have to convert a char* (from a C function) to long. At the moment
 I'm using
 
 long foo = to!long( to!string(bar) );


 but this doesn't feel right... with 2 to calls. Is this the way to go?
 Or is there something better?
 
 Mars


 This seems to work:
 
 char[] c = "123\0".dup;
 auto l = parse!long(c);
 writeln( l );


Yeah, but note that that's really equivalent to

auto foo = to!long(to!(char[])(bar));

except that you're creating an extra variable and using parse with its 
somewhat different semantics. In either case, you need to convert it from a 
char* to an actual character array of some kind before converting it to a 
long, and that means that you're allocating memory. In general, I would 
recommend just doing what the OP said

auto foo = to!long(to!string(bar));

It's the cleanest solution IMHO, and in general, that extra bit of memory 
allocation isn't a big deal. However, if you know the length of the char*, 
then you can slice it and pass that to std.conv.to. e.g.

auto foo = to!long(bar[0 .. 3]);

But you have to know the length of the string already - or use strlen on it to 
get its length. e.g.

auto foo = to!long(bar[0 .. strlen(bar)]);

It's quite doable and probably faster than converting to string and then to 
long, but it's certainly uglier code. This should only be a problem when 
interfacing with C though, since you really shouldn't be using char*'s or 
null-terminated strings otherwise.

- Jonathan M Davis

mta`chrono <chrono mta-international.net> writes:

Why not just go the "good old" way? you char* should be zero terminated
when coming from c.

====
private import  core.stdc.stdlib,
                std.stdio;

void main()
{
    const(char)* str = "1234567890".ptr;
    long lng = atoll(str);
    writeln(lng);
}
====

"Mars" <- -.-> writes:

Thanks for the replies, everyone.I guess I'll go with the double 
conversion for now.