Ptrdiff_t
ptrdiff_t is a signed integer type capable of representing the difference between pointers to elements of the same array.
Modern C, Third Edition
ptrdiff_t is a signed integer type capable of representing the difference between pointers to elements of the same array.
- How it is used
- Represents signed differences between pointer positions or sizes when an ordinary int may be too narrow.
- How deep it goes
- Defines the type, states the same-array constraint, gives the index-difference rule, and demonstrates subtraction without developing implementation details.
- Examples
- Uses two pointers into a four-element double array and verifies that subtracting their positions produces −2.
- What you can do after
- Evaluate pointer-position differences correctly and encode signed position or size differences with ptrdiff_t.
Modern C
ptrdiff_t is a signed integer type capable of representing the difference between pointers to elements of the same array.
- How it is used
- Uses ptrdiff_t to represent large differences that bear a sign, especially differences between pointers to array elements.
- How deep it goes
- Defines the type, recommends when to use it, and stops short of explaining pointer subtraction mechanics.
- Examples
- Contrasts signed pointer differences with sizes, cardinalities, and ordinal numbers.
- What you can do after
- Evaluate whether a difference requires a signed type and select ptrdiff_t instead of size_t when it does.
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