Thread: Deleting first character of an array

Suppose we have:

char myString[] = "This is a test";

If I want to delete the first character of an array, I am always tempted to do:
myString1++

The above doesn't work. What does work however is:


char* myString1 = myString + 1;


What makes this even more contradictory is that "The name of an array usually evaluates to the address of the first element of the array,"

Why doesnt the first line of code work?

The name of an array usually evaluates to the address of the first element of the array, but what it doesn't do is evaluate to a modifiable address. Defining a separate pointer, though, gives you something you can move. (EDIT: So you can use its value, but you cannot put it on the left side of an =, and you are doing that [implicitly] with ++.)

If you could evaluate an array name to a modifiable address, you would only lose the reference to the original element which isn't a disaster.

But then the compiler wouldn't be able to easily free all the memory it allocated and would probably cause memory leaks. By the way if you had dynamically allocated the memory for that array changing where that pointer points would likely cause a memory leak as well.

Originally Posted by Vespasian_2

I understand. Is there any design rationale behind this (Edit: I mean why was the language designed like this)? If you could evaluate an array name to a modifiable address, you would only lose the reference to the original element which isn't a disaster.

This is true for every variable.

Code:

int a; \\a particular memory slot is set aside for a
int *b = &a;  \\b can be set to point wherever you want it to point
&a = &b; \\ERROR: can't move actual variable a
&b = b + 1; \\ERROR: can't move actual variable b
b = b + 1; \\fine: changes the value of b so it points to the "next" memory space.

There's no reason to believe that your variables live in places that have addresses, necessarily.

Originally Posted by tabstop

This is true for every variable.

Code:

int a; \\a particular memory slot is set aside for a
int *b = &a;  \\b can be set to point wherever you want it to point
&a = &b; \\ERROR: can't move actual variable a
&b = b + 1; \\ERROR: can't move actual variable b
b = b + 1; \\fine: changes the value of b so it points to the "next" memory space.

There's no reason to believe that your variables live in places that have addresses, necessarily.

Ah I never saw it that way. Interesting, makes sense now that I think about it.