Stanford -- programming paradigms [lesson 6]
About symmetry of responsibility:
the lecturer writes an int version of Stack and then write a generic version of Stack
the int version's stackPop() interface is like this:
int stackPop(Stack* s);
but the generic version of Stack doesn't return the void* type like the int one did:
void stackPop(Stack* s, void* elemAddr);
Quote some words from the lecturer about this:
This used to be int. If I wanted to I could have punted on this right here and just passed in
one argument. And I could have returned a void * that pointed to a dynamically allocated
element that’s elemSize bytes wide. And I just would have copied not into elemAddr, but
into the result of the malloc call. With very few exceptions, malloc and strdup and realloc
being them, you usually don’t like a function to dynamically allocate space for the call
and then make it the responsibility of the person who called the function to free it.
There’s this asymmetry of responsibility, and you try to get in the habit as much as
possible of making any function that allocates memory be the thing that deallocate’s it as
well. There’s just some symmetry there and it’s just easier to maintain dynamically
allocated memory responsibilities.
本文探讨了在栈的数据结构实现中如何保持责任对称性,特别是在泛型版本的栈中如何处理内存分配与释放的问题。通过对比整型栈与泛型栈的不同实现方式,讲师强调了一般原则:分配内存的函数也应负责释放该内存。
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