Pset 2 vigenere uppercase the cipher

Question

So Im trying to make the cipher uppercase the cipher. I think that'll save a lot of hassle with if isupper else blah blah.

So I made a function

int uppercase(string a);

int uppercase(string a) {
for (int i = 0, n = strlen(a); i < n; i++) {
  toupper(a[i]);
}

Then I declared a function

string c = uppercase(argv[1]);

Then cycle through c[j], while making a loop like this

for (int i = 0, int j = 0, n = strlen(s); i < n; i++, j++)

So 2 questions here. Im getting an error like this

warning: incompatible integer to pointer conversion
  initializing 'string' (aka 'char *') with an expression of type 'int'
  [-Wint-conversion]
string c = uppercase(argv[1]);

How would I fix this

Question 2, is it even possible to have two integers looping like I did above? as in i++ j++

Answer 1

Look at what this line of code does:

string c = uppercase(argv[1]);

It declares c as a string, or more specifically, a pointer to a character string. The function uppercase() that you declared retruns an integer. This statement is trying to assign an integer to a pointer. That just doesn't work.

And yes, it is possible to increment two vars in a for loop.

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