A Structured Value Concept: Auxiliary Functions (STIL). Some constraints are to be imposed on the structured values of Exercise:

1. A vector value must consist of at least two elements.

2. The element values of a vector value must all be of the same type.

3. The indexes of a vector value must form a dense set of integers: If i and j are indexes of a vector value, then for all integers k properly between i and j , k is also an index of the vector value.

4. A record value must consist of at least two fields, that is, each with their (distinct) field identifier. Narrate and formalise the functions necessary to express the above.