Programming Forums > Application Development > C++

lepricaun · Aug 13th, 2004, 6:03 AM

i've made my own copy of the tool "echo", this is not to improve it or anything, but only to learn about strings and pointers...

(Toggle Plain Text)

#include <stdio.h>
#include <strings.h>
#include <stdlib.h>

int main(int argc,char** argv[])
{
  if(argc>1)
  {
    char *str[100];/*one array for every argument*/
    char *str2=" ";
    int loop=0;
    int count=1;
    
    while (loop<=argc)/*loop to copy every argument to a string[]*/
    {
      str[loop]=argv[count];
      loop++;
      count++;
    }
      
    for(loop=0;loop<argc-1;loop++)/*loop to print the strings with a space between them(just like they were entered)*/
    {
      printf("%s",str[loop]);
      printf("%s",str2);
    }    
    return 0;
  }
  return EXIT_FAILURE;
}

now the question: what can i do to improve this code? isn't there a possibility to read argv[1] as one complete string, even if a space is entered?

Kylixen · Aug 13th, 2004, 8:15 AM

Quote:

Originally posted by lepricaun@Aug 13 2004, 11:03 AM
i've made my own copy of the tool "echo", this is not to improve it or anything, but only to learn about strings and pointers...

(Toggle Plain Text)

#include <stdio.h> #include <strings.h> #include <stdlib.h> int main(int argc,char** argv[]) { if(argc>1) { char *str[100];/*one array for every argument*/ char *str2=" "; int loop=0; int count=1; while (loop<=argc)/*loop to copy every argument to a string[]*/ { str[loop]=argv[count]; loop++; count++; } for(loop=0;loop<argc-1;loop++)/*loop to print the strings with a space between them(just like they were entered)*/ { printf("%s",str[loop]); printf("%s",str2); } return 0; } return EXIT_FAILURE; }

#include <stdio.h> #include <strings.h> #include <stdlib.h> int main(int argc,char** argv[]) { if(argc>1) { char *str[100];/*one array for every argument*/ char *str2=" "; int loop=0; int count=1; while (loop<=argc)/*loop to copy every argument to a string[]*/ { str[loop]=argv[count]; loop++; count++; } for(loop=0;loop<argc-1;loop++)/*loop to print the strings with a space between them(just like they were entered)*/ { printf("%s",str[loop]); printf("%s",str2); } return 0; } return EXIT_FAILURE; }

now the question: what can i do to improve this code? isn't there a possibility to read argv[1] as one complete string, even if a space is entered?

(Toggle Plain Text)

#include <stdio.h>

int main(int argc, char *argv[]){

  int i;

  for(i = 1;i < argc;i++){

    printf("%s", argv[i]);

  }

  printf("\n");

}

lepricaun · Aug 13th, 2004, 8:59 AM

Quote:

CODE
#include <stdio.h>

int main(int argc, char *argv[]){

int i;

for(i = 1;i < argc;i++){

printf("%s", argv[i]);

}

printf("\n");

}

yes, stupid me, this would be enough too!
only thing:
printf("%s", argv[i]);

i would change into :
printf("%s ", argv[i]);

cause then the problem of the space is solved...

great, guess i didn't had to make it this difficult

kurifu · Aug 13th, 2004, 1:39 PM

Since no one else fielded the post increment operators on loop and count

(Toggle Plain Text)

count++;
loop++;

I will field that.

As it ends up post increment operators are actually very inefficient. You chould have used the following code:

(Toggle Plain Text)

    while (loop<=argc)/*loop to copy every argument to a string[]*/
    {
      str[loop++]=argv[count++];
    }

If you are using a post-increment operator on an operand in which the pre-incremented value is no being used in the same line, then you are wasting memory and time since a post increment operator will actually instantiate a copy of the variable, increment the original and return the copy.. kind of like this: (I will use a template so that I can demonstrate the generic use of the operator when showing my point)

(Toggle Plain Text)

//post increment operator...
template< classname typeT >
typeT operator++( typeT &lhv, typeT )
{
   typeT temp = lhv;
   lhv += 1;
   return temp;
}

//preincrement operator
template< classname typeT >
typeT &operator++( typeT &rhv )
{
   rhv += 1;
   return rhv;
}

Also as you can see due to the nature of the post and pre increment operators a second parameter (which fortunatly does not have to even be initialized) must be present for a post increment.

lepricaun · Aug 14th, 2004, 8:28 AM

see, there's the difference between me (newbie) and you (proffesional programmer), i don't understand what the f**k you are talking about

but eventually i will, i just have to practice/learn and be patient.

( i just started programming 2 months ago

)

kurifu · Aug 15th, 2004, 5:46 PM

I fyou do a google such for the C++ FAQ Lite, you will actually find that point, and a few other very good points covered which touch on topics of robustness and optimization, perhaps it could explain that a little bit more.

You will eventually though come to a point where you will consider all points such as that when tackling a project

No worries..

lepricaun · Aug 16th, 2004, 4:17 AM

thanks, i will do that

Aug 13th, 2004, 6:03 AM	#1
lepricaun Hobbyist Programmer Join Date: Aug 2004 Location: The Netherlands Posts: 111 Rep Power: 5	i've made my own copy of the tool "echo", this is not to improve it or anything, but only to learn about strings and pointers... (Toggle Plain Text) #include <stdio.h> #include <strings.h> #include <stdlib.h> int main(int argc,char** argv[]) { if(argc>1) { char str[100];/one array for every argument/ char str2=" "; int loop=0; int count=1; while (loop<=argc)/loop to copy every argument to a string[]/ { str[loop]=argv[count]; loop++; count++; } for(loop=0;loop<argc-1;loop++)/loop to print the strings with a space between them(just like they were entered)/ { printf("%s",str[loop]); printf("%s",str2); } return 0; } return EXIT_FAILURE; } #include <stdio.h> #include <strings.h> #include <stdlib.h> int main(int argc,char** argv[]) { if(argc>1) { char str[100];/one array for every argument/ char str2=" "; int loop=0; int count=1; while (loop<=argc)/loop to copy every argument to a string[]/ { str[loop]=argv[count]; loop++; count++; } for(loop=0;loop<argc-1;loop++)/loop to print the strings with a space between them(just like they were entered)/ { printf("%s",str[loop]); printf("%s",str2); } return 0; } return EXIT_FAILURE; } now the question: what can i do to improve this code? isn't there a possibility to read argv[1] as one complete string, even if a space is entered? __________________ http://www.white-scorpion.nl

Aug 13th, 2004, 1:39 PM	#4
kurifu Expert Programmer Join Date: Jul 2004 Location: Halifax, Nova Scotia (Canada) Posts: 784 Rep Power: 5	Since no one else fielded the post increment operators on loop and count (Toggle Plain Text) count++; loop++; count++; loop++; I will field that. As it ends up post increment operators are actually very inefficient. You chould have used the following code: (Toggle Plain Text) while (loop<=argc)/loop to copy every argument to a string[]/ { str[loop++]=argv[count++]; } while (loop<=argc)/loop to copy every argument to a string[]/ { str[loop++]=argv[count++]; } If you are using a post-increment operator on an operand in which the pre-incremented value is no being used in the same line, then you are wasting memory and time since a post increment operator will actually instantiate a copy of the variable, increment the original and return the copy.. kind of like this: (I will use a template so that I can demonstrate the generic use of the operator when showing my point) (Toggle Plain Text) //post increment operator... template< classname typeT > typeT operator++( typeT &lhv, typeT ) { typeT temp = lhv; lhv += 1; return temp; } //preincrement operator template< classname typeT > typeT &operator++( typeT &rhv ) { rhv += 1; return rhv; } //post increment operator... template< classname typeT > typeT operator++( typeT &lhv, typeT ) { typeT temp = lhv; lhv += 1; return temp; } //preincrement operator template< classname typeT > typeT &operator++( typeT &rhv ) { rhv += 1; return rhv; } Also as you can see due to the nature of the post and pre increment operators a second parameter (which fortunatly does not have to even be initialized) must be present for a post increment. __________________ Clifford Matthew Roche <geek@cliffordroche.com> Web Hosting: http://www.crd-hosting.com Consulting: http://www.crdev-consulting.com

Aug 14th, 2004, 8:28 AM	#5
lepricaun Hobbyist Programmer Join Date: Aug 2004 Location: The Netherlands Posts: 111 Rep Power: 5	see, there's the difference between me (newbie) and you (proffesional programmer), i don't understand what the f**k you are talking about but eventually i will, i just have to practice/learn and be patient. ( i just started programming 2 months ago ) __________________ http://www.white-scorpion.nl

Aug 15th, 2004, 5:46 PM	#6
kurifu Expert Programmer Join Date: Jul 2004 Location: Halifax, Nova Scotia (Canada) Posts: 784 Rep Power: 5	I fyou do a google such for the C++ FAQ Lite, you will actually find that point, and a few other very good points covered which touch on topics of robustness and optimization, perhaps it could explain that a little bit more. You will eventually though come to a point where you will consider all points such as that when tackling a project No worries.. __________________ Clifford Matthew Roche <geek@cliffordroche.com> Web Hosting: http://www.crd-hosting.com Consulting: http://www.crdev-consulting.com

Aug 16th, 2004, 4:17 AM	#7
lepricaun Hobbyist Programmer Join Date: Aug 2004 Location: The Netherlands Posts: 111 Rep Power: 5	thanks, i will do that __________________ http://www.white-scorpion.nl

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Programming Forums > Application Development > C++

String And Pointer Questions