Types describe expressions. As is standard in statically-typed programming languages, they are used only for validation purposes and have no real effect on the "output" of a program. The following table gives the grammar of types T. The section on expressions will give the meanings of types in terms of which expressions have which types.
Syntax |
Description |
Symbol |
Extern type |
[T] |
List of Ts |
T1 -> T2 |
Function from T1 to T2 |
[P] |
Action allowed only when P is satisified; requires no environment variables on input and writes none of its own |
[P] {CSymbol1 : T1, ..., CSymbolN : TN} |
Action that requires environment variables CSymbol1, ..., CSymbolN to have the given types when run |
[P] {CSymbol1_1 : T1_1, ..., CSymbol1_N : T1_N} => {CSymbol2_1 : T2_1, ..., CSymbol2_M : T2_M} |
Like the last case, but the second set of typed environment variables describes what the action will write |
P => T |
A nested action that requires that its nested configuration satisfy P; T should be some action type |
(T) |
Grouping |