program6_10.c

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/* Program 6.10 Analyzing text */
#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include <ctype.h>

#define TEXTLEN  10000      /* Maximum length of text            */
#define BUFFERSIZE 100      /* Input buffer size                 */
#define MAXWORDS   500      /* Maximum number of different words */
#define WORDLEN     15      /* Maximum word length               */

int main(void)
{
  char text[TEXTLEN+1];
  char buffer[BUFFERSIZE];
  char endstr[] = "*\n";          /* Signals end of input       */

  const char space = ' ';
  const char quote = '\'';

  char words[MAXWORDS][WORDLEN+1];
  int nword[MAXWORDS];            /* Number of word occurrences */
  char word[WORDLEN+1];           /* Stores a single word       */
  int wordlen = 0;                /* Length of a word           */
  int wordcount = 0;              /* Number of words stored     */


  printf("Enter text on an arbitrary number of lines.");
  printf("\nEnter a line containing just an asterisk to end input:\n\n");

  /* Read an arbitrary number of lines of text */
  while(true)
  {
    /* A string containing an asterisk followed by newline */
    /* signals end of input                                */
    if(!strcmp(fgets(buffer, BUFFERSIZE, stdin), endstr))
      break;

    /* Check if we have space for latest input */
    if(strlen(text)+strlen(buffer)+1 > TEXTLEN)
      {
        printf("Maximum capacity for text exceeded. Terminating program.");
        return 1;
      }
    strcat(text, buffer);
  }

  /* Replace everything except alpha and single quote characters by spaces */
  for(int i = 0 ; i < strlen(text) ; i++)
  {
    if(text[i] == quote || isalnum(text[i]))
      continue;
    text[i] = space;
  }

  /* Find unique words and store in words array */
  int index = 0;
  while(true)
  {
    /* Ignore any leading spaces before a word */
    while(text[index] == space)
      ++index;

    /* If we are at the end of text, we are done */
    if(text[index] == '\0')
      break;

    /* Extract a word */
    wordlen = 0;          /* Reset word length */
    while(text[index] == quote || isalpha(text[index]))
    {
      /* Check if word is too long */
      if(wordlen == WORDLEN)
      {
        printf("Maximum word length exceeded. Terminating program.");
        return 1;
      }
      word[wordlen++] = tolower(text[index++]);  /* Copy as lowercase     */
    }
    word[wordlen] = '\0';                        /* Add string terminator */

    /* Check for word already stored */
    bool isnew = true;
    for(int i = 0 ; i< wordcount ; i++)
      if(strcmp(word, words[i]) == 0)
      {
        ++nword[i];
        isnew = false;
        break;
      }

    if(isnew)
    {
      /* Check if we have space for another word */
      if(wordcount >= MAXWORDS)
      {
        printf("\n Maximum word count exceeded. Terminating program.");
        return 1;
      }

      strcpy(words[wordcount], word);   /* Store the new word  */
      nword[wordcount++] = 1;           /* Set its count to 1  */
    }
  }

  /* Output the words and frequencies */
  for(int i = 0 ; i<wordcount ; i++)
  {
    if( !(i%3) )                       /* Three words to a line */
      printf("\n");
    printf("  %-15s%5d", words[i], nword[i]);
  }

  return 0;
}