How do I modify an input through multiple functions in C++? - c++

Question

Basically I have to encode a name into a Soundex Code. The helper functions I implemented do the following:
Discard all non-letter characters from the surname: dashes, spaces, apostrophes, and so on.
Encode each letter as a digit
Coalesce adjacent duplicate digits from the code (e.g. 222025 becomes 2025).
Replace the first digit of the code with the first letter of the original name, converting to uppercase.
Remove all zeros from the code.
Make the code exactly length 4 by padding with zeros or truncating the excess.
Excuse the implementation of the helper functions, I know they could be implemented better. But when I manually pass the output from one function to another I see that the result is what I want. It's only when I combine them all into one function that I see that the output I pass is as if I didn't modify the input I passed at all. I believe my issue might have to do with passing by reference but doing that for all my functions made no difference or gave an incorrect output.
#include <iostream>
#include <string>
string removeNonLetters(string s) {
string result = "";
for (int i = 0; i < s.length(); i++) {
if (isalpha(s[i])) {
result += s[i];
}
}
return result;
}
string encode(string name) {
std::transform(name.begin(), name.end(), name.begin(), ::toupper);
string encoded = "";
for (int i = 0; i < name.size(); ++i) {
if (name[i] == 'A' || name[i] == 'E' || name[i] == 'I' || name[i] == 'O' || name[i] == 'U' || name[i] == 'H' || name[i] == 'W' || name[i] == 'Y')
encoded += '0';
else if (name[i] == 'B' || name[i] == 'F' || name[i] == 'P' || name[i] == 'V')
encoded += '1';
else if (name[i] == 'C' || name[i] == 'G' || name[i] == 'J' || name[i] == 'K' || name[i] == 'Q' || name[i] == 'S' || name[i] == 'X' || name[i] == 'Z')
encoded += '2';
else if (name[i] == 'D' || name[i] == 'T')
encoded += '3';
else if (name[i] == 'L')
encoded += '4';
else if (name[i] == 'M' || name[i] == 'N')
encoded += '5';
else if (name[i] == 'R')
encoded += '6';
}
return encoded;
}
string removeDuplicate(string encoded) {
for (int i = 0; i < encoded.size(); ++i) {
if (encoded[i] == encoded[i+1])
encoded[i] = '\0';
}
return encoded;
}
string removeZeros(string digits) {
for (int i = 0; i < digits.size(); ++i) {
if (digits[i] == '0')
digits[i] = '\0';
}
return digits;
}
string padding(string output) {
int size = output.size();
if (size < 4) {
for (int i = size; i < 4; ++i)
output += '0';
}
else if (size > 4) {
for (int j = size; j > 3; --j)
output[j] = '\0';
}
return output;
}
/* TODO: Replace this comment with a descriptive function
* header comment.
*/
string soundex(string s) {
/* TODO: Fill in this function. */
string copy = s;
removeNonLetters(s);
encode(s);
removeDuplicate(s);
s[0]= copy[0];
removeZeros(s);
padding(s);
return s;
}
int main() {
string s = "Curie";
cout << soundex(s) << '\n';
// Output should be C600 but I keep getting "Curie."
}

Answer 1

Your functions return the adjusted strings, that's good. But your calling code doesn't use the returned values!
Something like this is what you want.
string soundex(string s) {
/* TODO: Fill in this function. */
string copy = s;
s = removeNonLetters(s);
s = encode(s);
s = removeDuplicate(s);
s[0] = copy[0];
s = removeZeros(s);
s = padding(s);
return s;
}
If you want to change the value of a variable you normally use =. I'm sure you know that but for some reason you forgot because functions are involved.