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Start of Chapter 27: Extensions |
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Back to §27.13. Implications |
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Onward to §27.15. Defining phrases in Inform 6 |
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§27.14. Using Inform 6 within Inform 7
The current Inform, "Inform 7", had a low-level precursor unsurprisingly called Inform, which ran through versions 1 to 6. What made Inform 6 low-level was that its style of coding was much more like traditional programming: it reads as a simple form of C, or an elaborate form of assembly-language, but with some interactive fiction tweaks.
That language is still used inside today's Inform project as a way to express very low-level operations. What happens to code like that is now very different (it is compiled into Inter, an intermediate-level representation used inside Inform, and no longer by the Inform 6 compiler). But the notation is the same, and the practical effect is that it is as if we are writing I6 code.
The final sections of this chapter show how such I6 code can be mixed directly in with natural-language source text. The remaining pages will therefore make little or no sense to those who do not already know I6 notation, and in any case, such programming is really a last resort - it is always best to write regular source text than to resort to so-called "inclusions" of I6. Ideally, all I6 content would be confined to extensions (and this may be mandated in future releases of Inform), and even writers of extensions are asked to pare down their usage of I6 to the minimum necessary.
The methods for incorporating I6 code into I7 have been designed with this in mind, that is, to encourage people to use I6 in as self-contained a way as possible: in particular to isolate the relatively few functions which need to be written in I6, and to give them natural language expression.
Finally, anyone hacking with I7 for a while is likely to become curious about the Basic Inform or Standard Rules extensions, and to look at the text which sets up the Inform language and world model. These extensions are, of course, no secret, but can be misleading to read. For one thing, they appear to have great freedom to set up the world model as it pleases, but in fact the I7 compiler may well crash unless certain things are done just so in the Standard Rules: they depend on each other.
Moreover, the Basic Inform and Standard Rules extensions use a number of syntaxes which are not documented in this chapter: these are constantly being altered, and it would not be safe to imitate them. Any I6-related syntax which is not documented in this chapter may be removed or changed in effect at any time without warning, for instance in an update of Inform to fix bugs.