new in pawno, help - Printable Version

new in pawno, help - Printable Version

+- SA-MP Forums Archive (https://sampforum.blast.hk)
+-- Forum: SA-MP Scripting and Plugins (https://sampforum.blast.hk/forumdisplay.php?fid=8)
+--- Forum: Scripting Help (https://sampforum.blast.hk/forumdisplay.php?fid=12)
+--- Thread: new in pawno, help (/showthread.php?tid=635911)

new in pawno, help - fiha4155 - 16.06.2017

Hello, I am new in pawno coding. My question is how this can happen;

Code:

public OnPlayerText(playerid, text[])
{
	print(text[0]);
	return 1;
}

it outputs the whole text. not the first character but when I try something like;

Code:

public OnPlayerText(playerid, text[])
{
    text[0] = tolower(text[0]);
    return 1;
}

it lowers only the first character. it confuses me like really much. as you can see in prints output, text[0] means all of the text but tolower lowers only the first character.

Also, I read tolower function's info on wiki. It says;

Quote:

This function changes a single character to lowercase.

So how can it understand I mentioned the first character of that string? text[0] is all of the text, not only the first character. It should give errors in my view.

can somebody help?

Re: new in pawno, help - Vince - 16.06.2017

This is a bit weird but if you try to print a string and you specify a start index then the string will be printed from that start index onward until a null-character is found. If you only want to print a single character you can try something like this:

PHP Code:



printf("%c", text[0])

In all other instances it will indeed return that single character.

Also the language is called Pawn. Pawno is an editor.

Re: new in pawno, help - fiha4155 - 17.06.2017

@Vince, how do you know if it represents a starting point or a single character? And also why do we use something like idx in strtok, strrest functions? You create new variable named idx with no value, use it as a &index in those functions. What does & mean before &index? If idx doesn't have a value then why we need to use it? I say it has no value because;

Code:

new cmd[128], idx;
	cmd = strtok(cmdtext, idx);

As you can see, after creating it, you set no value to it. You use directly in strtok function.

btw, info of strtok:

Quote:

This (strtok) is used to search a string and find a variable typed after a " " (space), then return it as a string.

So if it finds the value after space and returns it, why do you need an additional second argument like idx? Let me explain what I say.

Code:

new 
     string[128],
     splitted[128]
;

string = "Hello world I am trying to understand pawn."

splitted = strtok(string,[IDK WHAT TO PUT HERE, IN MY VIEW YOU DONT NEED TO PUT SOMETHING])

splitted must be "world I am trying to understand pawn." because strtok found the thing after the space and returned it. Am I wrong?

I would be really happy if you answer all of these.

Re: new in pawno, help - Vince - 17.06.2017

The ampersand (&) means that a variable is passed "by reference" which means the function can alter the original variable. Unlike variables that are passed "by value" (the default) where - in a sense - a copy of the original variable is sent instead. For example:

PHP Code:



main()
{
    new byref;
    printf("%d", byref); // prints 0
    DoSomethingWithByRef(byref);
    printf("%d", byref); // prints 5
}

DoSomethingWithByRef(&value)
{
     value = 5;
}

In the case of strtok, the idx (index) variable stores the position where a space was encountered. So if strtok is called again with the same idx parameter (which now does have a value) it will start its search from that position onward. However, strtok is horribly outdated. Don't use it. Use sscanf instead.

Re: new in pawno, help - DRIFT_HUNTER - 17.06.2017

Quote:

@Vince, how do you know if it represents a starting point or a single character?

Since Vince didnt actually answered these (he did but not in a way you expect since it was in his first post). You dont know if its starting point or a single character. You pass starting address, function that formats or prints string just starts from there and goes up until it gets to a null character or hits array size limit (pawn keeps track of these at compilation time).

Re: new in pawno, help - OneDay - 18.06.2017

PHP Code:



native print(string []);

native tolower(char);

that is how to know - the functions are different parameters

Re: new in pawno, help - fiha4155 - 18.06.2017

Guys, I thank you very much I get it all now. Thanks especially to Vince. OneDay, thank you for showing up them. DRIFT_HUNTER I understood what you mean too, thanks. Let me ask one more question. How can we compare two strings?

Code:

(string[index] > ' ')

like in strtok function. It is a bit awkward.

Re: new in pawno, help - Dayrion - 18.06.2017

You can use strcmp (called str(->ing)cmp(->comparision)). Take a look on the wiki for futher details : https://sampwiki.blast.hk/wiki/Strcmp
A basically example:

PHP Code:



if(strcmp("hey", string) == 0)
...

If you want to compare 2 caracter, which is not the same thing, you need to compare the ASCII code of those 2 characters (All character there: http://www.ascii-code.com/).

Re: new in pawno, help - fiha4155 - 18.06.2017

Quote:

Originally Posted by Dayrion

You can use strcmp (called str(->ing)cmp(->comparision)). Take a look on the wiki for futher details : https://sampwiki.blast.hk/wiki/Strcmp
A basically example:

PHP Code:



if(strcmp("hey", string) == 0)

...

If you want to compare 2 caracter, which is not the same thing, you need to compare the ASCII code of those 2 characters (All character there: http://www.ascii-code.com/).

I get what you say, but my question was isn't it a bit awkward to say like "a character is bigger than a space". How pawn compare them itself? With comparing the ASCII numbers of them?

Re: new in pawno, help - DRIFT_HUNTER - 18.06.2017

Quote:

Originally Posted by fiha4155

I get what you say, but my question was isn't it a bit awkward to say like "a character is bigger than a space". How pawn compare them itself? With comparing the ASCII numbers of them?

Yes, just compare characters as integers.
By the way, with strcmp, there is a small logic stupidity. If strings are same, function will return 0. If first string finishes before its completely compared to second one, it will return -1, or 1 if second string finished before first. But, what if one of them is empty (length is 0)? Well function will return 0 (as if the strings were the same).

Re: new in pawno, help - fiha4155 - 18.06.2017

Quote:

Originally Posted by DRIFT_HUNTER

Yes, just compare characters as integers.

By the way, with strcmp, there is a small logic stupidity. If strings are same, function will return 0. If first string finishes before its completely compared to second one, it will return -1, or 1 if second string finished before first. But, what if one of them is empty (length is 0)? Well function will return 0 (as if the strings were the same).

Oh okay then, thank you very much.

Re: new in pawno, help - BigETI - 18.06.2017

If you wonder why strcmp is implemented to return 0, -1 or 1, it is actually useful for sorting.