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Monday, July 30, 2007

How String Functions Work? Part II

This is the second part of the article How String Functions (strinh.h) Work?

Here we'll be designing our own version of some other commonly used standard library string manipulation function that we discussed in the article String Manipulation Functions (string.h) II.

These will help increase your programming skills further.

mystrlwr():


  // mystrlwr function
  #include<iostream.h>

  // -- FUNCTION PROTOTYPES --
  char *mystrlwr(char *);
  // --       ENDS          --

  void main()
  {
    char ch[]="C++ ProGramming123";

    cout<<mystrlwr(ch);
  }

  char *mystrlwr(char *str)
  {
    char *temp;
    temp=str;

    while(*str!='\0')
    {
      // change only if its a
      // UPPER case character
      // intelligent enough not to
      // temper with special 
      // symbols and numbers
      if(*str>=65 && *str<=90)
        *str+=32;
      str++;
    }
    return temp;;
  }

mystrupr():


  // mystrupr function
  #include<iostream.h>

  // -- FUNCTION PROTOTYPES --
  char *mystrupr(char *);
  // --       ENDS          --

  void main()
  {
    char ch[]="C++ ProGramming123";

    cout<<mystrupr(ch);
  }

  char *mystrupr(char *str)
  {
    char *temp;
    temp=str;

    while(*str!='\0')
    {
      // change only if its a
      // UPPER case character
      // intelligent enough not to
      // temper with special 
      // symbols and numbers
      if(*str>=97 && *str<=122)
        *str-=32;

      str++;
    }
    return temp;
  }

mystrncat():


  // mystrncat- function 
  #include<iostream.h>

  void mystrncat(char *,const char *,int);

  void main(void)
  {
    char ch[]="This is great!";
    char ch2[25]="Yes ";
    mystrncat(ch2,ch,6);

    cout<<ch;
    cout<<endl;
    cout<<ch2;
  }

  void mystrncat(char *str1,const char *str2,int n)
  {
    int i=0;
    int len=0;

    // skip to the end of the first
    // string(target)
    while(str1[len]!='\0')
      len++;

    // start copying 'n' characters
    // from the start of the 
    // second string (source)
    // to the end of the
    // first (target)
    while(i<n)
    {
      str1[len]=str2[i];
      i++;len++;
    }
    str1[len]='\0';
  }

mystrncpy():


  // mystrncpy- function 
  #include<iostream.h>

  void mystrncpy(char *,const char *,int);

  void main(void)
  {
    char ch[]="This is great!";
    char ch2[20];

    mystrncpy(ch2,ch,6);

    cout<<ch;
    cout<<endl;
    cout<<ch2;
  }

  void mystrncpy(char *str1,const char *str2,int n)
  {
    int i=0;

    // copy 'n' characters
    // from str2 to str1
    while(i<n)
    {
      str1[i]=str2[i];
      i++;
    }
    // put the end of 
    // string identifier
    str1[i]='\0';
  }

mystrrev():


  // mysrtrev function

  #include<iostream.h>

  char *mystrrev(char *);

  void main(void)
  {
    char ch[]="Programming";
    cout<<mystrrev(ch);

    cout<<ch;
  }

  char *mystrrev(char *str)
  {
    char temp;
    int len=0;
    int i,j;

    // find the length
    while(str[len]!='\0')
      len++;

    j=len-1;

    for(i=0;i<len/2;i++)
    {
      // interchange the
      // characters from
      // the beginning to 
      // the end
      temp=str[j];
      str[j]=str[i];
      str[i]=temp;
      j--;
    }

    return str;
  }

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