Question

C++

When running my tests for my char constructor the assertion is coming back false and when printing the string garbage is printing that is different everytime but i dont know where it is wrong

Requirements:

• You CANNOT use the C++ standard string or any other libraries for this assignment, except where specified.
• You must use your ADT string for the later parts of the assignment.
• using namespace std; is stricly forbiden. As are any global using statements.
• Name the folder for this project: string (please use all lower case letters).
• Milestone 1
  • Implementation:
    • Create an ADT String using the class construct. It will be a NULL (zero) terminating charater array.
    • Note: C++ has a standard type called string so you should not use this name. Use String instead.
    • Please name all your files using only lower case letters.
    • Use the provided specification (svn/shared/project2/string-mile1.hpp) for naming your class and methods You should rename this to string.hpp. A test suite will be provided in Part 2 that uses this interface to test your string class.
    • You should use a fixed sized array of char for storage with a max capacity based on a constant const int STRING_SIZE = 256; This array will store the characters along with the NULL (0) terminator.
    • Implement the constructor functions (i.e., for char[] and char).
    • Overload + and += as concatenation (make sure they works for all variations string + string, string + char[], char[] + string, etc).
    • Overload all the relational operators (==, <, >, etc.).
    • Implement the methods:
      • operator[](int) - both accessor and modifier versions
      • length() - returns number of characters in string
      • capacity() - returns the max number of characters that can be stored in the string
      • substr(int start, int end) - returns the sub string from start to end position (inclusive)
      • findch(int pos, char ch) - returns location of ch at or after pos, returns -1 if not found
      • findstr(int pos, cosnt String& str) - returns the location of str at or after pos, returns -1 if not found.
      • Overload both I/O operators - Input should read in one word at a time. The input operator for char[] works that way and can be used.
  • Testing:
    • Develop a set of test cases, using asserts, for each of the operators and methods of the String class.
    • Write test cases first. Testing must be thorough. You will be relying on the string to be correct.
    • The command make tests will build and run the unit tests.
    • After each function passes a test, commit your work to svn with a message such as "Constructor tests passed".
    • Your string class will be tested on a set of cases developed by the instructors. You will be graded on how well you pass the instructor tests. These tests cover the required constructors and operators.
• Milestone 2
  • Implementation:
    • Re-implement your String class to use a dynamically allocated array for storage. Just as in the previous version, it will be a NULL terminating charater array.
    • Use the provided specification (svn/shared/project2/string-mile2.hpp) for naming your class and methods You should rename this to string.hpp.
    • This dynamic version of the String will only allocate exactly the amount of memory necessary to store the charaters. That is, the length will be the same as the capacity. However, the size of the dynamic array needs to have an extra char for the NULL terminator.
    • You will need to re-write your constructors to allocate the correct amount of memory.
    • The default constructor should allocate an array of size 1 for the empty string. The other constructors will allocate memory as needed. For example for String str("abc"); str.capacity() == 3, str.length() == 3, and str.stringSize == 4.
    • Implement a destructor, copy constructor, constant time swap, and assignment operator for your ADT. Also re-implement += to deal with the dynamic aspects.
    • You will also have to update concat/operator+() to return the proper sized string result.
    • Implement a private method resetCapacity to change the capacity of your string while keeping the contents intact. That is, create a new array and copy contents over to the new array, making sure to clean up memory.
    • Additionally, implement two private constructors that will be useful for managing memory. String(int) creates a String of capacity n and length 0. String(int, const char[]) creates a string of capacity n with an initial value of the char[] (and length equal to the char[]). Both of these constructors break the class invariant and thus are private for use by the class only.

============================================================================

string.hpp:

#ifndef CS23001_STRING_INTERFACE_HPP
#define CS23001_STRING_INTERFACE_HPP

#include <iostream>


////////////////////////////////////////////////////
// CLASS INV: str[length()] == 0             &&
//            length()      == capacity()    &&
//            capacity()    == stringSize - 1
//
class String {
public:
            String        ();                               //Empty string
            String        (char);                           //String('x')
            String        (const char[]);                   //String("abc")
            String        (const String&);                  //Copy Constructor
            ~String       ();                               //Destructor
    void    swap          (String&);                        //Constant time swap
    String& operator=     (String);                         //Assignment Copy
    char&   operator[]    (int);                            //Accessor/Modifier
    char    operator[]    (int)                     const;  //Accessor
    int     capacity      ()                        const;  //Max chars that can be stored (not including null)
    int     length        ()                        const;  //Actual number of chars in string
    String  operator+     (const String&)           const;
    String& operator+=    (const String&);
    bool    operator==    (const String&)           const;
    bool    operator<     (const String&)           const;
    String  substr        (int, int)                const;  //The sub-string from staring position to ending position
    int     findch        (int,  char)              const;  //Find location of charater starting at a position
    int     findstr       (int,  const String&)     const;  //Find location of str starting at a position
    void    test_String   ();
    friend  std::ostream& operator<<(std::ostream&, const String&);
    friend  std::istream& operator>>(std::istream&, String&);


private:

  String (int n );                                               //String(10) - capacity 10, empty string


    String (int , const char []);                          //String(10, "abc") - capacity 10 with "abc"
                    

  void    resetCapacity (int);                            //Resets capacity to N, keeps string intact
   


    char    *str;                                           //Pointer to char[]
    int     stringSize;                                     //Size includes NULL terminator
};

String  operator+       (const char[],  const String&);
String  operator+       (char,          const String&);
bool    operator==      (const char[],  const String&);
bool    operator==      (char,          const String&);
bool    operator<       (const char[],  const String&);
bool    operator<       (char,          const String&);
bool    operator<=      (const String&, const String&);
bool    operator!=      (const String&, const String&);
bool    operator>=      (const String&, const String&);
bool    operator>       (const String&, const String&);

#endif

============================================================================

string.cpp:

#include <iostream>
#include "string.hpp"
#include <cassert>

String::String() {            // default constructor - empty string
  stringSize = 1;
  str = new char [stringSize];
  str[0] = 0;
}

String::String(char ch) {   
  stringSize = 2;
  str = new char [stringSize];
  str[0] = ch;
  str[1] = '\0';
}

//REQUIRES: str.length() < capacity()
//String a("abc")
//Takes character array and turns into string array
String::String(const char X[]) {
  int i = 0;
  while (X[i] != '\0') ++i;
    stringSize = i;
    str = new char [stringSize + 1];
    for(int j = 0; j < capacity(); ++j)
      str[i] = X[i];
}

String::String(const String& rhs) {   //copy constructor
  stringSize = rhs.stringSize;
  str = new char [stringSize];
  for(int i = 0; i < capacity(); ++i)
    str[i] = rhs.str[i];
}

String::~String() {    //destructor
  delete[] str;
}

void String::swap (String& rhs) {    //Constant time swap
  char * temporary = str;
  str = rhs.str;
  rhs.str = temporary;
  int hold = stringSize;
  stringSize = rhs.stringSize;
  rhs.stringSize = hold;
}

String& String::operator= ( String rhs) {    // Assignment copy
  if (str == rhs.str) return *this;  //check to see if they are already pointing to the same address
  delete [] str;
  stringSize = rhs.stringSize;
  str = new char [stringSize];
  for (int i = 0; i < capacity(); ++i)
    str[i] = rhs.str[i];
  return *this;
}

//REQUIRES: 0 <= i < length()
// operator[] const --- allows access to const objects
char String::operator[](int i) const {
  assert( (i > 0) && (i < length()) );
  return str[i];
}

//REQUIRES: 0 <= i < length()
// operator[]       --- allows access / modification to non-const objects
char& String::operator[] (int i) {
  assert( (i >= 0) && (i < length() ) );
  return str[i];
}

int String::capacity() const {    //capacity = stringSize -1;
  return (stringSize - 1);
}

//ENSURES: Retval == i where str[i] = 0
int String::length() const {
  int result = 0;
  while (str[result] != '\0') 
    ++result;
  return result;
}

// retval == "xyzabc" where "xyx" + "abc"
String String::operator+(const String& rhs) const {
  String result;
  int offset= length();
  int i=0;
  while(rhs.str[i]!= '\0'){
    result.str[offset + i]= rhs.str[i];
    ++i;
    if(offset + i == capacity()) break;
  }
  result.str[offset + i]=0;
  return result;
}

String operator+(char lhs, const String& rhs) {
  return String(lhs) + rhs;
}

String operator+(const char lhs[], const String& rhs) {
  return String(lhs) + rhs;
}

String& String::operator+=(const String& rhs) {
  *this = operator+(rhs);
  return *this;
}

bool String::operator==(const String& rhs) const {
  int i = 0;
  while ((str[i] != '\0') && (str[i] == rhs.str[i])) ++i;
  return str[i] == rhs.str[i];
}

bool operator==(char lhs, const String& rhs) {
  return String(lhs) == rhs;
}

bool operator==(char lhs[], const String& rhs) {
  return String(lhs) == rhs;
}

bool String::operator<(const String& rhs) const {
  int i = 0;
  while ((str[i] != 0) && (rhs.str[i] != 0) && (str[i] == rhs.str[i])) ++i;
  return str[i] < rhs.str[i];
}

bool operator<(char lhs, const String& rhs) {
  return String(lhs) < rhs;
}

bool operator<(const char lhs[], const String& rhs) {
  return String(lhs) < rhs;
}

bool operator!=(const String& lhs, const String& rhs) {
  return !(lhs == rhs) || (lhs == rhs);
}

bool operator<=(const String& lhs, const String& rhs) {
  return (lhs < rhs) || (lhs == rhs);
}

bool operator>(const String& lhs, const String& rhs) {
  return (rhs < lhs);
}

bool operator>=(const String& lhs, const String& rhs) {
  return !(lhs < rhs);
}

std::ostream& operator<<(std::ostream& out, const String& rhs) {
  out << rhs.str;
  return out;
}

std::istream& operator>>(std::istream& in, String& rhs) {
  char placehold[540000];
  in >> placehold;
  rhs = String(placehold);
  return in;
}


//REQUIRES: 0 <= start < length()
//ENSURES:  retval == i where str[i] == ch && i >= start
//          or retval == -1 if ch != s[start.length()-1]
int String::findch(int start, char ch) const {
  if ( (start < 0) || (start >= length()) ) return -1;
  int i = start;
  while (str[i] != 0) {
    if (str[i] == ch) return i;
    ++i;
  }
  return -1;
}

/*
int String::findch(char ch) const { 
  return findch(0, ch); 
}
*/



int String::findstr(int pos, const String& rhs) const {
  int i = pos;
  if ((pos < 0) || (pos >= length() - rhs.length()))
    return -1;
  if (length() < rhs.length())
    return -1;

  while ((str[pos] != 0) && (rhs.length() + pos - 1 <= length())) {
    if (rhs == substr(i, i + rhs.length() - 1))
      return pos;
    ++i;
  }
  return -1;
}

//REQUIRES: 0 <= start <= end < length()
//ENSURES:  retval == s[start, ..., end]
String String::substr(int start, int end) const {
  if (start < 0) return String();
  if (start > end) return String();
  if (end >= length()) return String();

  String result;
  int i = start;
  while (i <= end) {
    result += str[i];
    ++i;
  }
  return result;
}

String::String (int n) {                                               //String(10) - capacity 10, empty string
  stringSize = n;
  str = new char [stringSize];
  str[0] = 0;
}

String::String (int n, const char ch[]) {                          //String(10, "abc") - capacity 10 with "abc"
  stringSize  = n;
  str = new char [n];
  for (int i = 0; i < n; ++i)
    str[i] = ch[i];
};                                                        

void    String::resetCapacity (int n ) {                            //Resets capacity to N, keeps string intact
  int smaller = stringSize;
  if (smaller > n) smaller = n;
  stringSize = n;
  char * tmp = new char [stringSize];
  for (int i = 0; i < smaller; ++i)
    tmp[i] = str[i];
  delete [] str;
  str = tmp;
}


void String::test_String() {
  String testing(5);
  assert(testing.length() == 0);
  assert(testing.capacity() == 5);

  String test(15);
  assert(test.length() == 0);
  assert(test.capacity() == 15);

  String tes(74);
  assert(test.length() == 0);
  assert(test.capacity() == 74);

  String CharArray(10, "abc");
  assert(CharArray.length() == 3);
  assert(CharArray.capacity() == 10);
}

============================================================================

Char constructor tests .cpp :

#include "string.hpp"
#include <cassert>
#include <iostream>

//===========================================================================
int main ()
{
  {
    //------------------------------------------------------
    // SETUP FIXTURE

    // TEST
    String  s = "A";

    // VERIFY
    assert(s == "A");
  }

  {
    //------------------------------------------------------
    // SETUP FIXTURE

    // TEST
    String  s = "B";
    std::cout<< s <<std::endl; ;
    // VERIFY
    assert(s == "B");
  }

  {
    //------------------------------------------------------
    // SETUP FIXTURE

    // TEST
    String  s = "n";

    // VERIFY
    assert(s == "n");
  }

  std::cout << "Done testing Charactor Constructor." << std::endl;

}

Answer 1

The constructor code has bugs. The fixed code for the problematic function is given below followed by the output snapshot. The buggy lines are commented out and the corrected lines follow it.

//REQUIRES: str.length() < capacity()
//String a("abc")
//Takes character array and turns into string array
String::String(const char X[]) {
int i = 0;
while (X[i] != '\0') ++i;
/* BUG:
stringSize = i;
str = new char [stringSize + 1];
for(int j = 0; j < capacity(); ++j)
    str[i] = X[i];
*/
// NEW CODE START
stringSize = i + 1; // i is the number of characters in the string, stringSize include the null
str = new char [stringSize];
for(int j = 0; j < capacity(); ++j)
    str[j] = X[j];
str[capacity()] = 0; // null terminate
//NEW CODE END
}