Modules¶
A Stratego program is organized as a collection of modules, which are imported from a main module.
Module Structure¶
module $ModuleName
$Imports*
$Section*
A module starts with a module header followed by a list of imports.
The name of a module in the header and imports should correspond to the file name, relative to a 'root' directory.
The rest of a module consists of signature, rules, and strategies sections, in any order, and possibly repeated.
File Name and File Extension¶
A module coincides with the file it resides in. It is not possible to define more than one module in a file, which precludes nested modules. The name of a module coincides with the file name, which should be fully qualified relative to a root directory.
A Stratego is a file with the extension .str2 for Stratego 2.
Modules for the Stratego 1 version of the language have extension .str.
The file extension does not feature in the module names used in the language.
The following is example module header:
module compilation/translation
imports desugaring/desugar
Module Names¶
Module names can be hierarchical. For example, consider the following directory structure
- trans
- compilation
- optimization.str2
- translation.str2
- desugaring
- desugar.str2
/ to indicate the directory structure, relative to a 'root' directory.
For example, if trans is declared as a root, then the module names for the modules above are
- compilation/optimization
- compilation/translation
- desugaring/desugar
Imports¶
imports $ModuleName+
A module should import all other modules from which it uses definitions. Imports are non-transitive and may be mutually recursive.
Modules can extend rule and strategy definitions from other modules. This allows the modular extension of a language.
When imported, all definitions in a module are visible. There are currently no mechanisms for hiding definitions.
An imports can list multiple modules.
The form
imports A B
is equivalent to
imports A
imports B
Signatures¶
A signature section introduces sorts, constructors, and overlays.
signature
sorts $Sort*
constructors
$ConstructorDef*
overlays
$OverlayDef*
Rules and Strategies¶
Rule definitions and strategy definitions introduce named transformations.
rules
$RuleDef*
strategies
$StrategyDef*
The rules and strategies section headers are indicative only; rule and strategy definitions can actually be mixed.
Libraries¶
A Stratego library is a closed collection of modules. A library can be pre-compiled since client programs may not extend its definitions. A library is used by importing a collection of external definitions of the signatures of constructors and transformations it defines. Even if definitions in a library are not included in a libraries external definition, they cannot be redefined, as that produces link errors.
Source Inclusion¶
Todo
Concrete Syntax¶
When using concrete syntax in a module, a .meta file accompanying the module indicates the parse table to use.
Created: October 17, 2024