Re: SYNTAX AND SEMANTICS

From:

benben <benhongh@yahoo.com.au>

Newsgroups:

comp.lang.c++

Date:

Sun, 28 May 2006 00:25:29 +1000

Message-ID:

<44786158$0$25129$afc38c87@news.optusnet.com.au>

Prof.Stanley wrote:

HELLO ALL I AM TRYING TO PUT UP A PROGRAM THAT DETECTS DOUBLE VOWELS
AFTER RECIEVING AN INPUT STRING; MY MAIN PROBLEM LIES IN THE INPUT CAN
SOMEBODY KINDLY HELP DETECT ANY SYNTAX OR SEMANTIC ERRORS:

HERE IS THE CODE:

#include <iostream>
#include <string>
#include <cctype>
using namespace std;

void scanner(char s[]);

void scanner(const char s[]);

bool isVowel(char);
int length(char s[]);

int length(const char s[]);

Const correctness matters.

int main(){

    //string sentence;
    const int max=4096;
    char sentence[max];
    cout << "Enter $ to terminate!" <<endl;
    do{
       cout << "\nEnter the input string: ";
       getline(sentence,max);
       scanner(sentence);
    }while(sentence != "$");

First off, you can't compare two raw strings with the != operator. You
should use std::strcmp:

     strcmp(sentence, "$")

or, since you are only interested in the first character:

     sentence[0] != '$'

Secondly, you should always check the stream state in a loop. Usually
I'd go with:

     while (cin)
     {
         cout << "blah";
         getline(sentence, max);

         if (sentence[0] != '$')
             scanner(sentence);
     }

At least you get the idea.

return 0;
}

void scanner(char s[]){

[260 lines of code snipped]

}

Wow! That function is way longer than it really should be. But before
giving any tips and hints I'm going to hit you with a number of compiler
error and logical errors.

One way to simplify design is to use the standard library facilities.
For example, a simple scanner can be trivially written as:

     void scanner(const char s[])
     {
         vector<char> vstack;
         map<string, unsigned int> m;
         unsigned int l = strlen(s);

         for (unsigned int i = 0; i <= l; ++i)
         {
             char c = s[i];

             if (isVowel(c))
             {
                 vstack.push_back(tolower(c, locale()));
             }
             else
             {
                 if (buff.size() == 2)
                 {
                     vstack.push_back(0);
                     ++m[&vstack[0]];
                 }

                 vstack.clear();
             }
         }

         // print out the content of m, left for exercise
     }

bool isVowel(char c){
     return (c == 'a' || c == 'A' || c == 'e' ||
      c == 'E' || c == 'i' || c == 'I' || c == 'o' ||
      c == 'O' || c == 'u' || c == 'U') ;
}

This function isn't lengthy but it is made very inflexible. Consider:

      static char vowels[] = "aeiouAEIOU";

      for (unsigned int i = 0; i < 10; ++i)
          if (c == vowels[i]) return true;

      return fail;

int length(char s[]){

int i=0;
while(s[i]='\0')
i=i+1;

return i;

}

That's just strlen...why do you reinvent the wheel?