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140 lines
8.3 KiB
Plaintext
Executable file
140 lines
8.3 KiB
Plaintext
Executable file
Title: The Inform 7 compiler
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Author: Graham Nelson
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@ The task of Inform to take natural-language source text, merged from the
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author's main source and some "extensions"; to compile that to an intermediate
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format called Inter; merge once again with pre-compiled libraries of Inter
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called "kits"; and then translate the result to a program which a
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more orthodox compiler can take the rest of the way. Because Inform 7 generates
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code for another compiler, rather than directly making an executable itself,
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it is properly speaking a "transpiler".
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For two decades that second compiler was always the roughly C-like Inform 6, a
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sturdy 1990s tool for generating interactive fiction "story files" which, after
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processing with the //inblorb// tool, can then be played in a web browser or
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with an "interpreter". In 2021, limited support was added for transpiling a
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general, non-IF-specific form of the language called Basic Inform to ANSI C.
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This can be compiled into more general executable programs using Clang, gcc,
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or other standard C compilers.
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= (hyperlinked text as BoxArt)
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main source text extension source texts
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\ /
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\ / INFORM7 Stage 1 or INBUILD
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\ /
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\|/ \|/
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syntax tree
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kit sources |
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(in Inform 6 code) | INFORM7 Stages 2 to 5
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INTER | |
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\|/ \|/
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precompiled Inter trees Inter tree
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\ /
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\ / INFORM7 Stage 6 or INTER
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\|/ \|/
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single linked Inter tree
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/ | \
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/ | \ INFORM7 Stage 7 or INTER
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\|/ \|/ \|/
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Inform 6 code C code index mini-website
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INFORM6 | | CLANG or GCC
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\|/ \|/
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story file executable
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INBLORB |
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\|/
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playable website
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=
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@ The Inform 7 transpiler, then, occupies the top two-thirds of the above diagram.
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Broadly speaking, it runs in seven stages, and the code for each stage is made
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up of one or more "modules", as follows:
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(*) Stage 1. A build manager called //supervisor// gathers what must be compiled.
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(*) Stage 2. //core// organises compilation of a single Inform project,
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doing little except to co-ordinate the other modules.
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(*) Stage 3. //assertions//, //values// and //knowledge// assemble a world model,
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turning sentences first into logical propositions and then into inferred facts,
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and also gather a set of rules and phrases to operate it. //if// and //multimedia//
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provide "plugins" to this process with additional features, adapting the language
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for interactive fiction.
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(*) Stage 4. //imperative// and //runtime// turn the constructs from Stage 3
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into an intermediate bytecode format called Inter.
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(*) Stage 5. //bytecode// and //building// manage and create Inter code. This is
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more of a layer than a stage, providing services to Stages 4, 6 and 7.
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(*) Stage 6. //pipeline// links and optimises this Inter code.
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(*) Stage 7. //final// generates final code and //index// generates human-readable
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Index pages, which forn a small website about the project.
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Inform 7 presents as three command-line tools, not one: //inbuild//, //inform7//
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and //inter//. Really, though, they are three points of access to the same code
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base. //inbuild// contains Stage 1 as a stand-alone tool, //inter// contains Stages
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5 to 7 as a stand-alone tool, and //inform7// is the entire compiler (Stages 1 to 7)
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in one. Each tool has its own CLI (or "command-line interface"): see
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//inbuild: Manual//, //inform7: Manual//, //inter: Manual// and
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//inbuild: Reference Card//, //inform7: Reference Card//, //inter: Reference Card//.
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The full breakdown of these three tools into modules is as follows:
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= (hyperlinked text as BoxArt)
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INBUILD INFORM7 INTER
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+-------------+ +-------------+ +-------------+
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| //inbuild// | | //inform7// | | //inter// |
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| (cli) | | (cli) | | (cli) |
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+-------------+ +-------------+ +-------------+
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. . . . . .
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+---------------------------+ . . . .
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| //supervisor//-module | . . . . } Stage 1
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+------------------------+ +------------------+ . .
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. . | //core//-module | . . } Stage 2
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. . | ------------------- | . .
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. . | //assertions//-module | . . }
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. . | //values//-module | . . } Stage 3
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. . | //knowledge//-module | . . }
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. . | //if//-module* | . . } * not used in
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. . | //multimedia//-module* | . . } Basic Inform
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. . | ------------------- | . .
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. . | //imperative//-module | . . } Stage 4
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. . | //runtime//-module | . . }
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. . +------------------+ +------------------------+
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. . . . | //bytecode//-module | }
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. . . . | //building//-module | } Stage 5
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. . . . | ------------------------- |
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. . . . | //pipeline//-module | } Stage 6
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. . . . | ------------------------- |
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. . . . | //final//-module | } Stage 7
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. . . . | //index//-module | }
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. . . . +---------------------------+
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. . . . . .
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+-----------------------------------------------------------------------+
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| SERVICES shared //linguistics//-module |
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| shared //calculus//-module |
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| shared //kinds//-module |
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| shared //lexicon//-module |
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| shared //inflections//-module |
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| shared //problems//-module |
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| shared //syntax//-module |
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| shared //words//-module |
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| shared //arch//-module |
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| shared //html//-module |
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+-----------------------------------------------------------------------+
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. . . . . .
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+-----------------------------------------------------------------------+
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| FOUNDATION //foundation//-module (in inweb repository) |
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| (Posix or Windows-related functions) |
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| (standard C library) |
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+-----------------------------------------------------------------------+
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=
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Note that all three tools use a "services" library, made up of a variety of modules
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providing services useful for natural language-based programs. At one time this
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was going to be called "Second Foundation" or possibly "Foundation and Empire",
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because there is also //foundation// underneath, a library of utility functions
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provided by //inweb//.
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@ That's a lot: for code-spelunkers, this is quite the limestone hillside of
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potential points of entry. Where to begin? Here are some suggested entrances:
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(a) See //supervisor: What This Module Does// for an overview of the
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build-management process.
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(b) Or take that on trust, and see //core: What This Module Does// for
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an overview of how Inform 7 basically works.
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(c) If you're more interested in the low-level representation of Inter code,
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and how to generate from it, see //bytecode: What This Module Does//.
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