www.digitalmars.com         C & C++   DMDScript  

digitalmars.D - writef is good, printf is bad

reply MicroWizard <MicroWizard_member pathlink.com> writes:
printf is old, bad and ugly. Theoretically it is correct. Let's try writef.
What should I do, when a char[] is actually empty (ie. null) ?

//char[] firstpart="kakukk";
char[] firstpart="";

printf("firstpart=%.*s\n",firstpart); //works, shows nothing after = sign

writefln("firstpart=%s",firstpart); //aborts and rewards with this message

Runtime error:
firstpart=Error: std.format formatArg

Could anybody show me a workaround?

Thanks in advance,
Tamas Nagy
Feb 20 2005
next sibling parent John Reimer <brk_6502 yahoo.com> writes:
On Sun, 20 Feb 2005 11:44:42 +0000, MicroWizard wrote:


 printf is old, bad and ugly. Theoretically it is correct. Let's try writef.
 What should I do, when a char[] is actually empty (ie. null) ?
 
 //char[] firstpart="kakukk";
 char[] firstpart="";
 
 printf("firstpart=%.*s\n",firstpart); //works, shows nothing after = sign
 
 writefln("firstpart=%s",firstpart); //aborts and rewards with this message
 
 Runtime error:
 firstpart=Error: std.format formatArg
 
 Could anybody show me a workaround?
 
 Thanks in advance,
 Tamas Nagy


I don't get that runtime error using writefln() with a firstpartk="". 
Works fine on dmd 0.113 on Linux.

My output:

firstpart =
Feb 20 2005
prev sibling next sibling parent Derek <derek psych.ward> writes:
On Sun, 20 Feb 2005 11:44:42 +0000 (UTC), MicroWizard wrote:


 printf is old, bad and ugly. Theoretically it is correct. Let's try writef.
 What should I do, when a char[] is actually empty (ie. null) ?
 
 //char[] firstpart="kakukk";
 char[] firstpart="";
 
 printf("firstpart=%.*s\n",firstpart); //works, shows nothing after = sign
 
 writefln("firstpart=%s",firstpart); //aborts and rewards with this message
 
 Runtime error:
 firstpart=Error: std.format formatArg
 
 Could anybody show me a workaround?
 
 Thanks in advance,
 Tamas Nagy


DMD v0.113

<code>
import std.stdio;

void main()
{
    char[] ns;
    char[] es = "";
    
    writefln("Empty String is '%s'", es);
    writefln("Null String is '%s'", ns);
    writefln("Lit Empty String is '%s'", "");
    ns = null;
    writefln("Lit Null String is '%s'", ns);
}
</code>

Output is ...

Empty String is ''
Null String is ''
Lit Empty String is ''
Lit Null String is ''

-- 
Derek
Melbourne, Australia
Feb 20 2005
prev sibling parent reply =?ISO-8859-1?Q?Anders_F_Bj=F6rklund?= <afb algonet.se> writes:
MicroWizard wrote:


 printf is old, bad and ugly. Theoretically it is correct. Let's try writef.
 What should I do, when a char[] is actually empty (ie. null) ?


It was impossible to guess from your sample code,
but "null" defaults to having a type of (void*)

In order for null to work with writef, it *must* have char[] type.
(I think this is a bug in Phobos, as it should accept "null" too ?)


 char[] firstpart="";
 writefln("firstpart=%s",firstpart); //aborts and rewards with this message
 
 Runtime error:
 firstpart=Error: std.format formatArg


As others shown, that code is working OK. You seem
to show output from another test program ? <aargh>

1.

     writefln("Null String is '%s'", null);


Null String is 'Error: std.format formatArg

2.

     writefln("Empty String is '%s'", "");


Empty String is ''

3.

     writefln("Null String is '%s'", cast(char[]) null);


Null String is ''


But just using "" instead of cast(char[]) null is a lot easier ?
Having a null char[] variable, instead of a literal, works too.

There are a still quite a few quirks in Phobos, regarding usage
of "" versus null. Hopefully they can all be sorted out in time...

--anders
Feb 20 2005
parent reply MicroWizard <MicroWizard_member pathlink.com> writes:
In article <cvabia$2vst$2 digitaldaemon.com>,
=?ISO-8859-1?Q?Anders_F_Bj=F6rklund?= says...

1.

     writefln("Null String is '%s'", null);


Null String is 'Error: std.format formatArg
2.

     writefln("Empty String is '%s'", "");


Empty String is ''


You got the point. I was too lazy to copy the code precisely.
The original type was byte[] and not char[] the automatic casting
works (somehow).


But just using "" instead of cast(char[]) null is a lot easier ?
Having a null char[] variable, instead of a literal, works too.

There are a still quite a few quirks in Phobos, regarding usage
of "" versus null. Hopefully they can all be sorted out in time...


Thanks a lot.
I agree, D should be grown up, and these anomalies will be solved.

Tamas Nagy
Feb 21 2005
parent =?ISO-8859-1?Q?Anders_F_Bj=F6rklund?= <afb algonet.se> writes:
MicroWizard wrote:


There are a still quite a few quirks in Phobos, regarding usage
of "" versus null. Hopefully they can all be sorted out in time...
 


 Thanks a lot.
 I agree, D should be grown up, and these anomalies will be solved.


Not a problem. There's another thread going in the bugs group
about the difference (or the lack thereof) between null and ""...

And I do think your subject should be "writef is D, printf is C".
Then again, to some people that seems to mean the same thing :-)

--anders
Feb 21 2005