Hi,

In this code, how can I cast the args[0] string to int for computing factorial(args[0])?

import std.stdio, std.bigint, std.string, std.conv, std.stream;

BigInt recFactorial(int n) {
if (n == 0)
return BigInt(1);
else
return (BigInt(n) * recFactorial(n - 1));
}

void main(string[] args) {
if (args.length == 2)
writeln("Factorial requires a number");
else
try {
writeln(recFactorial(cast(int) args[1]));
} catch {
writeln("Error");
}
}



I receive:
$ gdmd-4.6 factorial.d
factorial.d: In function ‘main’:
factorial.d:15:0: error: cannot cast expression of type string to int


Thanks in advance,
Xan.

On 2/2/12 1:35 PM, xancorreu wrote:
> In this code, how can I cast the args[0] string to int for computing
> factorial(args[0])?

std.conv.to!int(…) or parse().

Hope this helps,
David

Use to!int(args[1])
> I receive:
> $ gdmd-4.6 factorial.d
> factorial.d: In function ‘main’:
> factorial.d:15:0: error: cannot cast expression of type string to int
> 
> 
> Thanks in advance,
> Xan.

Al 02/02/12 16:58, En/na David Nadlinger ha escrit:
> On 2/2/12 1:35 PM, xancorreu wrote:
>> In this code, how can I cast the args[0] string to int for computing
>> factorial(args[0])?
>
> std.conv.to!int(…) or parse().

to!int gives me this error:

$ ./factorial 222
Factorial requires a number



parse() where is the doc?

Thanks in advance,
Xan.
>
> Hope this helps,
> David

On Thursday, 2 February 2012 at 16:21:39 UTC, xancorreu wrote:
> $ ./factorial 222
> Factorial requires a number

args[0] is the name of your program.
(The first thing you typed on the command
line.)

Use args[1] to get that number.

> parse() where is the doc?

http://www.d-programming-language.org/phobos/std_conv.html#parse


to!int(args[1]) is probably what you want here though.

Al 02/02/12 16:58, En/na David Nadlinger ha escrit:
> On 2/2/12 1:35 PM, xancorreu wrote:
>> In this code, how can I cast the args[0] string to int for computing
>> factorial(args[0])?
>
> std.conv.to!int(…) or parse().

Sorry, if condition was wrong. conv.to!int is perfect!

Thanks,
>
> Hope this helps,
> David

Why cast(int) does not work and I have to call another function?

Thanks,

Al 02/02/12 17:24, En/na Adam D. Ruppe ha escrit:
> On Thursday, 2 February 2012 at 16:21:39 UTC, xancorreu wrote:
>> $ ./factorial 222
>> Factorial requires a number
>
> args[0] is the name of your program.
> (The first thing you typed on the command
> line.)
>
> Use args[1] to get that number.
>
>> parse() where is the doc?
>
> http://www.d-programming-language.org/phobos/std_conv.html#parse
>
>
> to!int(args[1]) is probably what you want here though.

I get "segment violation" error with  ./factorial 400000
How can I resolve it?

My code is:

import std.stdio, std.bigint, std.string, std.conv, std.stream;

BigInt recFactorial(int n) {
    if (n == 0)
        return BigInt(1);
    else
        return (BigInt(n) * recFactorial(n - 1));
}

void main(string[] args) {
    if (args.length != 2)
        writeln("Factorial requires a number");
    else
        try {
            writeln(recFactorial(std.conv.to!int(args[1])));
        } catch {
            writeln("Error");
        }
}



Thanks a lot,

On 02-02-2012 17:26, xancorreu wrote:
> Why cast(int) does not work and I have to call another function?
>
> Thanks,
>
> Al 02/02/12 17:24, En/na Adam D. Ruppe ha escrit:
>> On Thursday, 2 February 2012 at 16:21:39 UTC, xancorreu wrote:
>>> $ ./factorial 222
>>> Factorial requires a number
>>
>> args[0] is the name of your program.
>> (The first thing you typed on the command
>> line.)
>>
>> Use args[1] to get that number.
>>
>>> parse() where is the doc?
>>
>> http://www.d-programming-language.org/phobos/std_conv.html#parse
>>
>>
>> to!int(args[1]) is probably what you want here though.
>

Because D is a strongly typed language. Casting a string to an int doesn't make sense from a type system perspective.

--
- Alex

Alex Rønne Petersen Wrote:

> On 02-02-2012 17:26, xancorreu wrote:
> > Why cast(int) does not work and I have to call another function?
> >
> > Thanks,
> >
> > Al 02/02/12 17:24, En/na Adam D. Ruppe ha escrit:
> >> On Thursday, 2 February 2012 at 16:21:39 UTC, xancorreu wrote:
> >>> $ ./factorial 222
> >>> Factorial requires a number
> >>
> >> args[0] is the name of your program.
> >> (The first thing you typed on the command
> >> line.)
> >>
> >> Use args[1] to get that number.
> >>
> >>> parse() where is the doc?
> >>
> >> http://www.d-programming-language.org/phobos/std_conv.html#parse
> >>
> >>
> >> to!int(args[1]) is probably what you want here though.
> >
> 
> Because D is a strongly typed language. Casting a string to an int doesn't make sense from a type system perspective.
> 
> --
> - Alex