2.3.20 Inc and Dec

INC and DEC statements have the form:

    INC(v, n)
    DEC(v, n)

where v designates a variable of an ordinal type and n is an optional integer-valued argument. If omitted, n defaults to 1. The statements increment and decrement v by n, respectively. The statements are equivalent to:

    WITH x = v DO x := VAL(ORD(x) + n, T) END
    WITH x = v DO x := VAL(ORD(x) - n, T) END

where T is the type of v and x stands for a variable that does not appear in n. As a consequence, the statements check for range errors.

In unsafe modules, INC and DEC are extended to ADDRESS.