§1. The inform7 tool is the active part of the Inform apps familiar to end users, but it can also be run as a command-line tool outside of the app. See the Manual (in inform7) and Reference Card (in inform7).
- ● The contents page for the inform7 web is here: inform7.
- ● The command-line interface for Inform as a stand-alone tool is implemented at Main (in inform7).
Note that the inform7 is the largest of the three compiler tools, since it contains the other two tools in their entirety.1 See inbuildn and intern for details of those. But inform7 also contains modules of its own which are not found elsewhere, and those are the ones described on this page. See structure for the bigger picture: the modules unique to inform7 perform just one simple-looking part of the compilation flow diagram —
syntax tree | | INFORM7 Stages 2 to 4/5 | \|/ Inter tree
§2. The core module is an organiser of what happens during Stages 2 to 5, which involve very many sub-stages. It includes a form of scheduler, queueing up individual tasks; it provides general mechanisms for issuing problem messages; and also a "plugin" architecture enabling language features to be added. Most Inform users think of rooms, map connections and so on as being built in to the language itself, but internally we take the view that there is a purist Basic Inform language dealing only in data, and then a set of optional compiler features to add domain-specific gadgets to that language.
- ● Contents page of web: core.
- ● Detailed overview: What This Module Does (in core).
§3. The assertions module looks at sentences in the source text outside of rules/phrases: often copular sentences like "X is a number which varies", but also imperative forms like "Understand ... as ..." or rule/phrase headers such as "To ...:".
- ● Contents page of web: assertions.
- ● Detailed overview: What This Module Does (in assertions).
§4. The values module parses descriptions of values and their kinds, and contains in particular the "S-parser" (parsing fragments of the AST called "specifications"), and the Inform typechecker, a behemoth of an algorithm called "Dash". Typechecking in Inform is quite unlike that used in most programming languages, partly because types are often only implied in the language, partly because natural language blurs lines between values and types considerably in any case.
- ● Contents page of web: values.
- ● Detailed overview: What This Module Does (in values).
§5. The knowledge module manages variables, properties, instances and so forth, and stores knowledge of differing certainty about their values in the form of "inferences".
- ● Contents page of web: knowledge.
- ● Detailed overview: What This Module Does (in knowledge).
§6. The imperative module is almost a compiler-within-a-compiler, since it parses and generates Inter code from the bodies of phrase and rule definitions. More modern compiler-concepts such as closures and generics do make tiny appearances here, but really it's an old-school imperative compiler.
- ● Contents page of web: imperative.
- ● Detailed overview: What This Module Does (in imperative).
§7. The runtime module generates Inter code for everything other than functions. This can be quite elaborate: whereas, say, a global variable in Inform is likely to need only a single Inter instruction, something like a various-to-various relation may need a large body of Inter arrays, properties or active code in order to function at runtime. runtime also writes copious and diligent metadata into the Inter tree, so that the index can later be generated, and to make the tree more fathomable to the code generator (or other pipeline stages) later on.
While it contains no tricky or controversial algorithms, this is in some ways the least satisfactory module in Inform, because it remains undecided exactly what developments in linking together Inform source text may follow. Developers should probably not assume that the conventions used by runtime are stable, for the moment.2
- ● Contents page of web: runtime.
- ● Detailed overview: What This Module Does (in runtime).
2 If we ever do go down the road of a full-on linker, issues like this would be part of what is nowadays called "ABI stability". ↩
§8. The if module consists of an extensive suite of features (see core above) to add interactive fiction support to the Basic Inform language. Support for scenes, a spatial map, a protagonist character, and so on are all to be found here.
- ● Contents page of web: if.
- ● Detailed overview: What This Module Does (in if).
§9. The multimedia module consists of a few features (see core above) to add images, sound files and external file-handling to the Basic Inform language.
- ● Contents page of web: multimedia.
- ● Detailed overview: What This Module Does (in multimedia).
§10. As noted above, inform7 contains many other modules: all of those from intern, all of those from inbuildn, and all of the services, together with the ubiquitous foundation library.