"The average operation" takes place on primitives. But even in languages where strings are treated as primitives, they're still arrays under the hood, and doing anything involving the whole string takes O(N) time, where N is the length of the string.
For example, adding two numbers generally takes 2-4 ASM instructions. Concatenating ("adding") two strings requires a new memory allocation and either one or two string copies, involving the entire string.
Certain language factors can make it worse. In C, for example, a string is simply a pointer to a null-terminated array of characters. This means that you don't know how long it is, so there's no way to optimize a string-copying loop with fast move operations; you need to copy one character at a time so you can test each byte for the null terminator.
It's anyways bad practice to initialie a char array with a string literal.
The author of that comment never really justifies it, and I find the statement puzzling.
In C (and you've tagged this as C), that's pretty much the only way to initialize an array of char
with a string value (initialization is different from assignment). You can write either
char string[] = "october";
or
char string[8] = "october";
or
char string[MAX_MONTH_LENGTH] = "october";
In the first case, the size of the array is taken from the size of the initializer. String literals are stored as arrays of char
with a terminating 0 byte, so the size of the array is 8 ('o', 'c', 't', 'o', 'b', 'e', 'r', 0). In the second two cases, the size of the array is specified as part of the declaration (8 and MAX_MONTH_LENGTH
, whatever that happens to be).
What you cannot do is write something like
char string[];
string = "october";
or
char string[8];
string = "october";
etc. In the first case, the declaration of string
is incomplete because no array size has been specified and there's no initializer to take the size from. In both cases, the =
won't work because a) an array expression such as string
may not be the target of an assignment and b) the =
operator isn't defined to copy the contents of one array to another anyway.
By that same token, you can't write
char string[] = foo;
where foo
is another array of char
. This form of initialization will only work with string literals.
EDIT
I should amend this to say that you can also initialize arrays to hold a string with an array-style initializer, like
char string[] = {'o', 'c', 't', 'o', 'b', 'e', 'r', 0};
or
char string[] = {111, 99, 116, 111, 98, 101, 114, 0}; // assumes ASCII
but it's easier on the eyes to use string literals.
EDIT2
In order to assign the contents of an array outside of a declaration, you would need to use either strcpy/strncpy
(for 0-terminated strings) or memcpy
(for any other type of array):
if (sizeof string > strlen("october"))
strcpy(string, "october");
or
strncpy(string, "october", sizeof string); // only copies as many characters as will
// fit in the target buffer; 0 terminator
// may not be copied, but the buffer is
// uselessly completely zeroed if the
// string is shorter!
Best Answer
If the language you are using supports the use of enums, I'd use them. It allows you to limit the number of options available for a given type. e.g. in Java: