Difference between "const text[]" and "text[]"?

Difference between "const text[]" and "text[]"? - Printable Version

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+--- Thread: Difference between "const text[]" and "text[]"? (/showthread.php?tid=368737)

Difference between "const text[]" and "text[]"? - [DOG]irinel1996 - 14.08.2012

Hi,
I have a little doubt between two things:

pawn Код:

stock MyFunc(playerid, const msg[]) //This one

stock MyFunc(playerid, msg[]) //And this

What's exatly the difference?
I know that const is for constant variables, that doesn't change their values.
So, what's its point there, in a stock?

Thank you!

Re: Difference between "const text[]" and "text[]"? - MicroD - 14.08.2012

Prevent arrays from being modified, with that const.

Код:

stock fail(const msg[])
{
    msg[0] = '0';
}

It will not be changed.

And it will cause error and warning:

Код:

error 022: must be lvalue (non-constant)
warning 215: expression has no effect

Re: Difference between "const text[]" and "text[]"? - IceMeteor - 14.08.2012

Quote:

Originally Posted by MicroD

Prevent arrays from being modified, with that const.

Код:

stock fail(const msg[])
{
    msg[0] = 0;
}

It will not be changed.

You mean changes like what?

Re: Difference between "const text[]" and "text[]"? - MicroD - 14.08.2012

Look:

Код:

main()
{
    fail("trol");
    win("trol");
}

stock fail(const msg[])
{
    msg[0] = 'r';
    print(msg); //Can not be printed because of error
}
ERROR

stock win(msg[])
{
    msg[0] = 'r';
    print(msg);//Will print rrol
}

Re: Difference between "const text[]" and "text[]"? - [DOG]irinel1996 - 14.08.2012

So, there isn't a huge difference, because if we do something as that:

pawn Код:

stock SendMsg(playerid, const msg[])
{
    new info[128];
    format(info,128,"INFO: %s",msg);
    SendClientMessage(playerid,-1,info);
    return 1;
}
//I think it's the same as this:
stock SendMsg(playerid, msg[])
{
    new info[128];
    format(info,128,"INFO: %s",msg);
    SendClientMessage(playerid,-1,info);
    return 1;
}

Re: Difference between "const text[]" and "text[]"? - MicroD - 14.08.2012

Yes, it is almost same. Only difference is that const.
It just prevent msg from being modified.

Re: Difference between "const text[]" and "text[]"? - SEnergy - 14.08.2012

Quote:

Originally Posted by irinel1996

So, there isn't a huge difference, because if we do something as that:

pawn Код:

stock SendMsg(playerid, const msg[])
{
    new info[128];
    format(info,128,"INFO: %s",msg);
    SendClientMessage(playerid,-1,info);
    return 1;
}
//I think it's the same as this:
stock SendMsg(playerid, msg[])
{
    new info[128];
    format(info,128,"INFO: %s",msg);
    SendClientMessage(playerid,-1,info);
    return 1;
}

except that you CAN'T change value of "msg" string

Re: Difference between "const text[]" and "text[]"? - [DOG]irinel1996 - 14.08.2012

OK guys, got it now.
Thank you!
Also, +

Re: Difference between "const text[]" and "text[]"? - Sinner - 14.08.2012

const(ant) is used when a certain parameter shoulden't be changed. Let's say a function uses a password, would you like that function to change the password while it's doing it's thing? No you woulden't, and to make sure you don't make a mistakes and accidentally change it you may use const.

pawn Код:

// You don't want this function to change the password
// That would be dramatic (just an example)
stock DoSomethingWithPassword(const password[]) {
    // Whatever this function does, it could never change the value of password[] since that value is now a constant
}

Re: Difference between "const text[]" and "text[]"? - [DOG]irinel1996 - 14.08.2012

Quote:

Originally Posted by Sinner

const(ant) is used when a certain parameter shoulden't be changed. Let's say a function uses a password, would you like that function to change the password while it's doing it's thing? No you woulden't, and to make sure you don't make a mistakes and accidentally change it you may use const.

pawn Код:

// You don't want this function to change the password
// That would be dramatic (just an example)
stock DoSomethingWithPassword(const password[]) {
    // Whatever this function does, it could never change the value of password[] since that value is now a constant
}

Changed how and by who? By mistake?