adding strings hard problem...

**jabka** · 04-22-2007

sorry if i do some thing wrong posting that code ..

anyway ..
as have been said before there are more then two ways to aproach this :
1. to convert the strings to int then do math stuff on it;
2. to work on strings (like i did);
3. more options .

if you prefear to work with numbers and not chars

[Qoute]
(int) char_varibale
[/Qoute]

but be aware that numbers more then 32K will have to be dobule and not int.
so you probably will need to some cutting on the string
look on what i posted and work around that.

p.s.
sorry if i misspell something (i don't know how to make my gcc warn my about English syntax errors ).

**jabka** · 04-22-2007

Originally Posted by quzah

Code:

signed int x = 'z' - '0';
if( x < 0 || x > 9 )
    puts( "You didn't enter a digit." );

That's what error checking is for. You could always just use isdigit.

Quzah.

better will be :

Code:

if !((x[i] >= '0') && (x[i ]<= '9'))
  printf("sorry mate but you have enterd a non digit value %c\n",x[i]);

**quzah** · 04-22-2007

A typecast won't make a '9' into a 9.

Quzah.

**nadroj** · 04-22-2007

Originally Posted by jabka

better will be :

both ways will work.

**quzah** · 04-22-2007

Originally Posted by jabka

better will be :

Code:

if !((x[i] >= '0') && (x[i ]<= '9'))
  printf("sorry mate but you have enterd a non digit value &#37;c\n",x[i]);

Even better would be if your example actually compiled. But we'll pretend it's a typo.

Quzah.

**nadroj** · 04-22-2007

quzah can you comment on post 15? thanks

edit: nevermind, i think what you mentioned was similar to what was just discussed. wow i am not thinking tonight.

**zacs7** · 04-22-2007

@nadroj,
quzah said to do error checking in that manor, not comparing each ascii character in a control then setting a variable to it's corresponding value.

Doing it the way you mention'd is rather crappy, considering if you had to do upto 255 comparisons.

**jabka** · 04-22-2007

Originally Posted by quzah

Even better would be if your example actually compiled. But we'll pretend it's a typo.

Quzah.

my bad lost the braces before the not ..

here is the compiled form ..

Code:

#include <stdio.h>

int main(){
	int i=0;
	char x[10] = {'0','1','2','a','4','5','6','7','8','x'};

	for (i = 0;i < 10; i++)
 	 if (!((x[i] >= '0') && (x[i] <= '9')))
   	   printf("non digit on : %d \n",i);

}

**nadroj** · 04-22-2007

of course you wouldnt have to do 255 comparisons. you compare 0 to 9.

**zacs7** · 04-22-2007

Who said you wouldn't?

If someone also wanted to allow the alphabet thats another 26 or 52 , but then they wanted to allow some special chars, its another n chars... It'd become very messy and bloated

**nadroj** · 04-22-2007

what we were discussing is how to convert the char to a number. the (poor) way that i was thinking to do it is you compare the character to each character '0' to '9', 10 comparisons. nothing about 255 comparisons or the alphabet. but i already know this is a efficient way to go.

**zacs7** · 04-22-2007

Yes I am aware of that, but every line of code you write should keep future modification in mind, especially if you work in a group.

However a look-up table could be considered a crude universal way of solving the problem, one may even call it a 'hack'.

**nadroj** · 04-22-2007

initially i said what i was going to do was going to be in a function, 'char2int'. which had that one purpose, so it wouldnt require future modification. but i agree that it is good practice to keep that in mind.

edit: in the event that mathematicians invent a new number, id be screwed though!

**quzah** · 04-22-2007

Originally Posted by zacs7

Yes I am aware of that, but every line of code you write should keep future modification in mind, especially if you work in a group.

However a look-up table could be considered a crude universal way of solving the problem, one may even call it a 'hack'.

If you're going to worry about future modifications, then a lookup table is a lousy way to go, since it would be locale specific.

Quzah.

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