# Forward Sequence

### Description

A Forward Sequence is a Sequence which guarantees that its elements are arranged in a definite order, and that the ordering will not change spontaneously [1]. Iterators into a forward sequence satisfy the Forward Iterator requirements.

### Refinement of

Sequence

### Valid expressions

Forward Sequence does not define any new expressions beyond those defined in Sequence. However, it refines the expression requirements.

Expression | Expression type
--- | ---
`typename begin<s>::type` | A model of Forward Iterator
`typename end<s>::type` | A model of Forward Iterator

### Invariants

For any forward sequence `s` the following invariants always hold:

- Two different iterations through `s` will access its elements in the same order.

### Models

- `vector`
- `vector_c`
- `list`
- `list_c`
- `range_c`

### Notes

[1] Both between compilation sessions and from iteration to iteration.

### See also

Sequence, Bidirectional Sequence, Forward Iterator

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Last edited July 15, 2002 2:34 pm