• Ludovic A. (12/12) Mar 19 2010 According to the documentation,main() must be declared using one of the
• bearophile (9/22) Mar 19 2010 In D1 Tango doesn't define the alias string that's char[]. But the (stri...
• Ludovic A. (1/1) Mar 19 2010 Ok this is what I thought. I filled an issue.
• Steven Schveighoffer (9/15) Mar 19 2010 You are allowed to modify the args, they are guaranteed not to be in ROM...
• bearophile (4/8) Mar 19 2010 In D2 all strings are immutable(somechartype)[], so how can you justify ...
• Steven Schveighoffer (9/18) Mar 19 2010 All string *literals* are immutable. The reason is so the runtime does ...

Ludovic A. <ludovica axis.com> writes:

According to the documentation,main() must be declared using one of the
following forms:

void main() { ... }
void main(char[][] args) { ... }
int main() { ... }
int main(char[][] args) { ... }

However with the latest D2 compiler I can write:
import std.stdio;

void main (string[] args) {
  writeln("main with string[]");
}

What's the trick?

bearophile <bearophileHUGS lycos.com> writes:

Ludovic A. Wrote:

 According to the documentation,main() must be declared using one of the
 following forms:
 
 void main() { ... }
 void main(char[][] args) { ... }
 int main() { ... }
 int main(char[][] args) { ... }

If you use "int main" then you have to add a return, possibly returning
std.c.stdlib.EXIT_SUCCESS or std.c.stdlib.EXIT_FAILURE. If you use void it uses
a EXIT_SUCCESS.


 However with the latest D2 compiler I can write:
 import std.stdio;
 
 void main (string[] args) {
   writeln("main with string[]");
 }

In D1 Tango doesn't define the alias string that's char[]. But the (string[]
args) can be used in D1 too, with Phobos:
http://codepad.org/wUC6N6LB

In D2 string means something different, it's immutable(char)[] that is a
mutable array of immutable chars. I hope Tango2 will define string the same way.
So in D1 (string[] args) is the same as (char[][] args), but in D2 they are a
little different things. Even if D2 accepts both forms, I think that modifying
the contents of args is not a good practice, so in D2 I suggest to use
(string[] args), that has immutable chars.
In practice in D2 you can even use main(immutable string[] args), that I think
is the best form :-)

Bye,
bearophile

Ludovic A. <ludovica axis.com> writes:

Ok this is what I thought. I filled an issue.

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

On Fri, 19 Mar 2010 06:23:36 -0400, bearophile <bearophileHUGS lycos.com>  
wrote:

 So in D1 (string[] args) is the same as (char[][] args), but in D2 they  
 are a little different things. Even if D2 accepts both forms, I think  
 that modifying the contents of args is not a good practice, so in D2 I  
 suggest to use (string[] args), that has immutable chars.
 In practice in D2 you can even use main(immutable string[] args), that I  
 think is the best form :-)

You are allowed to modify the args, they are guaranteed not to be in ROM.   
The true signature, if there existed such a thing, should be  
unique(char[])[] args.  Because D arrays are safe, you are in no danger of  
corrupting memory, unlike C.

However, the docs should be updated to add the string[] variant, I agree  
with that.

-Steve

bearophile <bearophileHUGS lycos.com> writes:

Steven Schveighoffer:
 You are allowed to modify the args, they are guaranteed not to be in ROM.   
 The true signature, if there existed such a thing, should be  
 unique(char[])[] args.  Because D arrays are safe, you are in no danger of  
 corrupting memory, unlike C.

In D2 all strings are immutable(somechartype)[], so how can you justify the
args[x] to be an exception to that rule?

Bye,
bearophile

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

On Fri, 19 Mar 2010 08:43:25 -0400, bearophile <bearophileHUGS lycos.com>  
wrote:

 Steven Schveighoffer:
 You are allowed to modify the args, they are guaranteed not to be in  
 ROM.
 The true signature, if there existed such a thing, should be
 unique(char[])[] args.  Because D arrays are safe, you are in no danger  
 of
 corrupting memory, unlike C.

 In D2 all strings are immutable(somechartype)[], so how can you justify  
 the args[x] to be an exception to that rule?

All string *literals* are immutable.  The reason is so the runtime does  
not have to use the heap every time you use a string literal.  You can  
certainly have/use mutable strings.  program arguments are runtime  
decided, and are passed in one place, so they do not have to be  
immutable.  Making them immutable, while possible and preferred by some,  
is not a requirement, and shouldn't be forced on the programmer.

-Steve