• Vaidas (4/15) Jun 27 2019 Is it possible to set the default values for the Main function's
• Adam D. Ruppe (10/12) Jun 27 2019 No, as far as the language is concerned, a value is always being
• wjoe (16/31) Jun 27 2019 consider this:
• Paul Backus (12/27) Jun 27 2019 Your main function is receiving an empty array as an argument,
• Paul Backus (4/12) Jun 27 2019 Correction: you should check for `args.length == 1`, since (as
• Vaidas (6/30) Jun 27 2019 I'm feeling, that overwriting the zero argument that is

Vaidas <vaidas.boqsc gmail.com> writes:

Is it possible to set the default values for the Main function's 
arguments?
It seems that I'm getting Range error.

import std.stdio : writeln;
void main(string[] args = ["asdsfasdf", "asdklfajsdk", 
"asdfasdfasd"]){
 
    writeln("", args[1]);
}

Output:
vaidas vaidas-SATELLITE-L855:~/Desktop$ rdmd newfile.d
core.exception.RangeError newfile.d(4): Range violation

----------------
??:? _d_arrayboundsp [0x555f5b79f8e9]
??:? _Dmain [0x555f5b79e7ee]

Adam D. Ruppe <destructionator gmail.com> writes:

On Thursday, 27 June 2019 at 17:05:05 UTC, Vaidas wrote:
 Is it possible to set the default values for the Main 
 function's arguments?

No, as far as the language is concerned, a value is always being 
passed from the operating system, so those default values would 
never trigger.

What you could do though is just check inside main:

void main(string[] args) {
    if(args.length <= 1) args = ["defaults", "here"];
}


Keep in mind that args[0] is almost always set to the name of the 
executable, so length == 0 is liekly never going to happen.

wjoe <invalid example.com> writes:

On Thursday, 27 June 2019 at 17:05:05 UTC, Vaidas wrote:
 Is it possible to set the default values for the Main 
 function's arguments?
 It seems that I'm getting Range error.

import std.stdio : writeln;
void main(string[] args = ["asdsfasdf", "asdklfajsdk", 
"asdfasdfasd"]){
 
    writeln("", args[1]);
}

 Output:
vaidas vaidas-SATELLITE-L855:~/Desktop$ rdmd newfile.d
core.exception.RangeError newfile.d(4): Range violation

----------------
??:? _d_arrayboundsp [0x555f5b79f8e9]
??:? _Dmain [0x555f5b79e7ee]


consider this:

module d-program;

void main(string[] args)
{
   import std.stdio;
   writeln("args = ", args);
}

---

~/> ./d-program abc def

Output:
args = ["~/d-program", "abc", "def"]

---

~/> ./d-program

Output:

args = ["~/d-program"]

Paul Backus <snarwin gmail.com> writes:

On Thursday, 27 June 2019 at 17:05:05 UTC, Vaidas wrote:
 Is it possible to set the default values for the Main 
 function's arguments?
 It seems that I'm getting Range error.

import std.stdio : writeln;
void main(string[] args = ["asdsfasdf", "asdklfajsdk", 
"asdfasdfasd"]){
 
    writeln("", args[1]);
}

 Output:
vaidas vaidas-SATELLITE-L855:~/Desktop$ rdmd newfile.d
core.exception.RangeError newfile.d(4): Range violation

----------------
??:? _d_arrayboundsp [0x555f5b79f8e9]
??:? _Dmain [0x555f5b79e7ee]


Your main function is receiving an empty array as an argument, 
which overrides the default argument.

The correct way to do what you want to do is this:

void main(string[] args)
{
     string[] defaultArgs = ["my", "default", "arguments"];
     if (args.length == 0) {
         args = defaultArgs;
     }
     // Process args...
}

Paul Backus <snarwin gmail.com> writes:

On Thursday, 27 June 2019 at 17:20:37 UTC, Paul Backus wrote:
 void main(string[] args)
 {
     string[] defaultArgs = ["my", "default", "arguments"];
     if (args.length == 0) {
         args = defaultArgs;
     }
     // Process args...
 }

Correction: you should check for `args.length == 1`, since (as 
Adam points out) the name of the program will be passed as 
args[0].

Vaidas <vaidas.boqsc gmail.com> writes:

On Thursday, 27 June 2019 at 17:22:36 UTC, Paul Backus wrote:
 On Thursday, 27 June 2019 at 17:20:37 UTC, Paul Backus wrote:
 void main(string[] args)
 {
     string[] defaultArgs = ["my", "default", "arguments"];
     if (args.length == 0) {
         args = defaultArgs;
     }
     // Process args...
 }

 Correction: you should check for `args.length == 1`, since (as 
 Adam points out) the name of the program will be passed as 
 args[0].

I'm feeling, that overwriting the zero argument that is 
containing the program's path is mostly never a good idea.

Here, zero argument will not be overwritten.

Program.d
import std.stdio : writeln;
void main(string[] args)
{
     string[] defaultArgs = [args[0], "default", "arguments"];
     if (args.length == 1) {
         args = defaultArgs;
     }
     // Process args...
     writeln("", args);
 }

Output:

vaidas vaidas-SATELLITE-L855:~/Desktop$ rdmd program.d
["/tmp/.rdmd-1000/rdmd-program.d-7E2D9881B29D67DB2D97D001FFD2817D/program",
"default", "arguments"]