From the input point of view, all these forms are correct. So only one intype, boolean , is enough to represent a boolean argument. Although the two types of types are semantically two different objects, syntactically they are very similar. Moreover, even the logical structure is very similar so, from now on, they will be treated as they are two variants of the same type. They are the simpler types one can use inside a TL program.
Compound types are a bit more complicated types.
They are record, case and list types whose elements are other types. These types of types are nearly impossible to be handled by hand, but can by easily coded by an interpreter. Introduction TL syntax is case insensitive , but the names of the identifiers are memorized as declared. As in most of the languages, also TL parsing is based on reserved words. Formal syntax Click here to see the formal syntax using YACC syntax.