9. Type Checking

With the addition of another type that can be mixed in, type checking becomes a necessity in Vcalc. This means ensuring that vectors and scalars are where they belong. Most expressions allow the interchange of vectors and scalars, but there are a few cases where it is necessary to have one or the other.

Note that these rules are already in their respective sections, this list just serves to bring further attention to where type checking is important.

• Ranges: lower and upper bounds must be integers.

• Conditional Statements: must be booleans (remember that integers can be implicitly downcast to booleans).

• Domains: in a domain expression (generator, filter, index) the domain must be a vector.

• Generators: the expression must be an integer (remember that booleans can be implicitly upcast to integers).

• Filters: the predicate must be a boolean (remember that integers can be implicitly downcast to booleans).