I am writing a program that needs to take text input, and modify individual characters. I am doing this by using an array of characters, like so:
char s[] = "test";
s[0] = '1';
cout << s;
(Returns: "1est")
But if I try and use a variable, like so:
string msg1 = "test";
char s2[] = msg1;
s2[0] = '1';
cout << s1[0]
I get an error: error: initializer fails to determine size of 's2'
Why does this happen?
C-style arrays require literal values for initialization. Why use C-style arrays at all? Why not just use std::string...
string msg1 = "test";
string s2 = msg1;
s2[0] = '1';
cout << s2[0];
The space for all the variables is allocated at compile time. You're asking the compiler to allocate space for an array of chars called s2, but not telling it how long to make it.
The way to do it is to declare a pointer to char and dynamically allocate it:
char *s2;
s2 = malloc(1+msg1.length()); // don't forget to free!!!!
s2 = msg1; // I forget if the string class can implicitly be converted to char*
s2[0] = '1'
...
free(s2);
I think char a[] can't be initialized by a string. Edit: "a string" is actually a c-type string (char array with '\0' at the end).
$8.5.1 and $8.5.2 talk about rules related to initialization of aggregates.
