Release notes for Inform v4.4 (build 4X60)

This release was made on 23 August 2007, before Inform was open-sourced. At that time versions of Inform were identified by build codes in the form NLNN.

This is part of the historical archive of release notes.

Overview

This build adds 19 new examples and modernises a dozen others, and presents a new volume of built-in documentation: the Inform Recipe Book. It also provides new features for variable text, improves and extends table-handling, allows Glulx-format games to read and write files and communicate with external programs, and allows extensions to create more readable and useful documentation.

Language

The "[one of]" text substitution previously provided by Jon Ingold's extension "Text Variations", which built on code by Andrew Plotkin and Roger Firth, has now been adopted into Inform's core language. Examples of its use include:

	say "You flip the coin. [one of]Heads[or]Tails[purely at random].";
	say "[one of]The phone rings[or]The phone rings a second time[or]The
		phone rings again[stopping].";
	say "You turn the light switch [one of]off[or]on[cycling]. Nothing
		happens.";
	say "The newspaper headline is: [one of]War Casualties
		[or]Terrorists[or]Banks[sticky random] [one of]Continue To Expand
		[or]Lose Out[sticky random].";
	say "The light changes randomly again; now it's [one of]green
		[or]amber[or]red[at random].";
	say "Zorro strides by, [one of]looking purposeful[or]grim-faced[or]deep
		in thought[or]suppressing a yawn[or]scratching his ribs[or]trying
		to conceal that he has cut himself shaving[as decreasingly
		likely outcomes].";
	say "You dip into the chapter on [one of]fish[or]mammals[or]birds
		[or]reptiles such as the black salamander[in random order]."

See the new section 5.6 in the documentation: note that "[as decreasingly likely outcomes]" and "[in random order]" are new options, the former using a tapering probability distribution, the latter a random permutation.

It should be noted that the new implementation of this substitution is completely different to the one provided by the extension. The previous method involved printing all the text to a buffer array, then hash-coding it and taking choices based on this hash, which meant that the same sequence of choices occurring twice in the same text would be effectively the same (because of having the same hash code); thus
```
	"This is [one of]A[or]B[at random] versus [one of]A[or]B[at random]."
```
could never print "This is A versus A." or "This is B versus B." The new implementation treats each "[one of]..." individually. To get around this, define
```
	To say A-or-B: say "[one of]A[or]B[at random]".
```
and then change the text to
```
	"This is [A-or-B] versus [A-or-B]."
```
Furthermore, there is no buffer array, no hash code, and it is no longer possible to extract state information by deliberately printing the text with an incomplete "[one of]" construction. (To quote the Text Variations documentation: "a terrible way to solve that kind of problem", so we don't feel too bad about withdrawing it.) Thus the phrases "the index of the last buffer" and "the index of the buffer" no longer exist. In any case, the new implementation polices the use of the construction so that leaving it incomplete is no longer possible. "[one of]" must be matched by one of its possible conclusions "[purely at random]", "[stopping]", ..., or problem messages will be generated; similarly, "[or]" can only legally be used inside the construction. On the other hand, the new implementation does allow the construction to be nested, both explicitly in a single text and also implicitly (where a text substitution inside one of the options itself does something which also involves a "[one of]"), where the old implementation would silently have failed. As an explicit example:
```
	"[one of]A palace on the [one of]Nile[or]Euphrates[purely at random]
	delta[or]A hovel by the [one of]Tigris[or]Rhine[purely at random]
	river[purely at random]."
```
In practice, if a work in progress used "Text Variations" and did not try to use "the index of the last buffer" then there is a good chance that simply deleting the line
```
	Include Text Variations by Jon Ingold.
```
will be the only change required. We thank Jon Ingold and his collaborators for donating their design. The extension "Text Variations" will continue to be available from the website for the time being, but marked as no longer needed or compatible with builds from here onwards. We suggest that users uninstall it once they are sure that any works in progress continue to work without. This change implements proposal (6.20) from the January 2007 consultation document.
The run-time code for handling tables has been rewritten to improve its reliability and efficiency. A number of minor bugs have been fixed in the process, notably a failure to sort correctly on tables which contain mixed blank and non-blank rows, and a rarely occurring problem to do with storing the number 32739 in table entries under the Z-machine.
Table sorting is now carried out using a hybrid algorithm: insertion sort from 1 to 11 rows, and in-place mergesort for 12 rows and up. This is much faster on even medium-sized tables (e.g. about ten times faster on tables of 200 rows), and is also stable in all cases: that is, if two rows have the same value in the X column of a table, and that table is then sorted (forwards or backwards) on the X column, then they will stay the same side as each other. As a consequence, all sorts are idempotent, that is, performing the same sort operation twice always results in the second operation making no changes at all. (The previous algorithm was idempotent but, owing to a bug, not in all cases stable.) Insertion/in-place mergesort was chosen because we needed stability, O(n log n) average running time (together with good performance on nearly-sorted tables, which are the commonest usage cases in actual Inform source text), O(1) storage overhead (the Z-machine is extremely short of table space), and reasonably predictable stack usage.
Projects compiled for Glulx rather than the Z-machine now have the ability to make use of external files. Like sound effects and figures, these are declared and given names before use:
```
	The File of Glaciers is called "ice".
```
This creates a new named constant "File of Glaciers" (whose kind of value is "external-file") for use in file contexts. (The prefix "binary file" rather than "file" can be used to make the file binary in the Glk sense, but the default is to use text files for all purposes.) Each file is considered to be owned by some project, identified by its IFID. By default, a newly declared file is owned by its own project, but we can also specify that we want to use somebody else's file, either explicitly or vaguely:
```
	The file of Spectral Sequences (owned by project
		"4122DDA8-A153-46BC-8F57-42220F9D8795") is called "adams".
	The file of Boundaries (owned by another project) is called "milnor".
```
We can write or append to a file owned by anyone, but can only read a file whose ownership matches this description. External files are indexed in the Contents index, alongside figures and sound effects. Files sometimes exist, and sometimes do not: they are sometimes complete, sometimes only partly written. (For a file shared between two games running simultaneously, one might try to read a file the other is still in the middle of writing.) We can test this with:
```
	if the file of Invariants exists...
	if ready to read the file of Invariants...
```
A file cannot be ready if it does not exist, so the latter is a stronger condition.
Tables can be saved to external files, and loaded them back in again, during play: all file-handling is done automatically. The user only needs to use the phrases:
```
	read the File of Glaciers into the Table of Antarctic Features;
	write the File of Glaciers from the Table of Antarctic Features;
```
Blank entries are preserved; it is legal to write a small file into a large table, and if so, all unwritten entries are blanked; a run-time problem is shown if the file contains more rows or columns than will fit into the table which it is being loaded into; similarly, a run-time problem is shown on trying to write a table which contains data not safely exchangeable with other story files (or other compilations of itself).
Text can also be saved to a file, and again all file-handling is automatic:
```
	write "Jackdaws love my big sphinx of quartz." to the file of
		Abecedary Wisdom;
	append "Jinxed wizards pluck ivy from the big quilt." to the file of
		Abecedary Wisdom;
```
The quoted text can, of course, contain substitutions, so can be long and complex if need be. On an append, the file is created if it does not already exist.

Text from a file is printed back with the text substitution:

	"[text of the File of Abecedary Wisdom]"

To copy one file to another, for instance,

	write "[text of the file of Abecedary Wisdom]" to the file of
		Secondary Wisdom;

The implications to do with lockability have been improved:
```
	A locked thing is usually lockable.
	A locked container is usually closed.
	A locked door is usually closed.
	A lockable container is usually openable.
	A lockable door is usually openable.
```
Thus writing "The ballot box is a locked container." will now deduce that the box is probably lockable, closed but openable. These are only guesses by Inform, and can be overridden by giving explicit instructions to the contrary: "The ballot box is a locked unopenable container."
Definitions of adjectives, which previously had to refer to their subjects only by the pronoun "it" (or in some cases "his", "her", etc.), can now make callings. For instance:
```
	Definition: a direction (called thataway) is viable if the
		room thataway from the location is a room.
```
is a good deal easier to read than
```
	Definition: a direction is viable if the room it from the location
		is a room.
```
which was previously the only way to write this. Only a single calling can be made, and it must refer to the specific object to which the definition applies.
A new rule in the Standard Rules, the "can only take things rule", prevents the taking of objects which are not things - for instance, rooms or directions. (Such an action can never normally be generated by the grammar for typed commands, but if Understand sentences are written to open the possibility then the player will see ugly "programming error" messages: the new rule prints a more suitable reply.) -Extension documentation can now request "paste into the source text" icons like those found in the main documentation and its examples. If an indented paragraph of quoted source text begins with an asterisk and then a colon, like so...
```
	*: A dog is a kind of animal.
```
...then the asterisk-and-colon are replaced in the final documentation by a paste icon: clicking this will insert the copy which follows into the source text. The text to be pasted is considered to begin after the colon, and to continue until the next unindented text, i.e., it can run for many quoted paragraphs, but as soon as the quotation is broken the paste extent will end. Any tables within the quoted range should be safely rendered with tabs in between the columns.
Large extensions which need to include a large amount of documentation can now subdivide it using headings and/or subheadings, like so:
```
	Chapter: Pesky Meddling Kids
	Section: Dog Food
```
A suitable table of contents with navigation links will be automatically added to the extension documentation, if so.
The Extensions chapter of the documentation has, appropriately enough, been extended: it now opens up a limited number of previously restricted syntaxes to public use. These will only be useful to experienced Inform 6 programmers.
Fixed a further namespace clash: a "let" name can now coincide with the column name of a table. (This was preventing John Clemens's extension "Scheduled Activities" from working in recent builds.)

Documentation, examples and extensions

A new manual, The Inform Recipe Book, has been added to the application. It sits alongside the previous manual (Writing with Inform) and presents the examples thematically, with connecting advice and comparisons of techniques to achieve a wide range of IF effects. This should make the (now 357) examples much easier to browse and to borrow from.

Examples

"Radio Daze" example from Jon Ingold's Text Variations extension brought into the main documentation.
"Camp Bethel" added to demonstrate several other common applications of text alternatives.
"Chanel version 1" added to demonstrate paired "[i]...[/i]" and "[b]...[/b]" italic and boldface tags, similar to HTML's.
"Blink" added to demonstrate creating one's own text variations keyed to values, using the special terminology explained in the Extensions chapter.
"Uncommon Ground" added to demonstrate creating one's own text variations keyed to the identity of the player character.
"Labyrinth of Ghosts" added to demonstrate recording the deaths of all previous players of the story file by storing them in a file.
"Alien Invasion Part 23" added to demonstrate saving preference files from one game in a series for use in the next episode.
"Flathead News Network" added to demonstrate communicating with a simple Unix script running in the background, in order to provide live news headlines (drawn from RSS feeds) inside a story file.
"Ferragamo Again", "Straw Boater" slightly cleaned up to be better filed in the Recipe Book.
"Cinco" edited to fix a particularly bone-headed bug that vitiated the whole point of the example.
"When?" adjusted to slightly improve the way the example is described.
"Modern Conveniences" added to demonstrate standard kitchen and bathroom appliances.
"Do Pass Go" added to demonstrate a pair of dice.
"Mirror, Mirror" added to demonstrate remembering the current room description by preserving it in an external file.
"The Unbuttoned Elevator Affair" added as an example of a simpler lift than the elaborate one in "Dubai".
"Further Reasons Why All Poets Are Liars" added as an example of using action variables for an action which moves a box around internal positions inside a location; a much thinner version of this example, "A pushable box", has been removed.
"M. Melmoth's Duel" added, similarly to replace "Tinted wallpaper".
"The Second Oldest Problem" added to demonstrate using action variables to make the going action react to moving between dark rooms.
"Saint Eligius" added to demonstrate an additional comment added to a room description when the player first enters.
"Baritone, Bass" added to demonstrate defining the character at the start of play.
"Bic" added to demonstrate testing whether any defined objects are missing description properties.
"Meet Market" added to demonstrate relations involving multiple values.
"Depth" rewritten to improve the simulated geometry used to test whether an item could fit inside a container.
"Patient Zero," "Today Tomorrow," "Reporting rules for other characters' behavior," "Uptown Girls", "Full Moon" edited to take advantage of new text variation features.
"Belfry", "Bikini Atoll", "Dearth and the Maiden", "Hayes Code", "Lies", "Safety", "Undertomb" and "Weathering" all made into formal numbered examples rather than, as in previous builds, appearing in the running text of the manual.

Extensions

"Basic Screen Effects" very slightly updated so that the documentation is clearer about the lack of colored letters in Glulx, and suggests that the author turn to Glulx Text Effects for these capabilities instead; also given a new example to demonstrate forcing the player to type what we want him to type (since this is becoming something of a frequently-asked question); chapter and section headings and paste-able examples added.
"Basic Help Menu", "Glulx Text Effects", "Locksmith", "Menus", "Punctuation Removal" tagged so that the example can be pasted.
"Complex Listing", "Plurality" tagged and given chapter and section headings.

Problem messages

Problem message added for trying to use "[something related by...]" to understand something which can have no relations.

Bug fixes

Bug fixed (or, if you prefer, feature added) whereby sentences providing alternative names for times of day, like:
```
	Understand "lunch time" as 11:30 am.
```
...now work as might be expected.
Bug fixed whereby Understand ... as a person would fail with I6 errors. (Apologies for this: an oversight in 4W37's abolition of the player-character kind, which had the same flaw, but nobody noticed because it was so little used.)
Bug fixed whereby "if S is not happening", for S a scene, would incorrectly think that a completed once-only scene was still happening.
Bug fixed whereby implications would in some cases be ignored in circumstances which it would be tiresome to write out, but to do with multiple things being simultaneously present, some qualifying and some not.
Bug fixed whereby using I7 to rerelease an existing I6 story file in blorbed format with bibliographic data would fail because of the lack of a room (needed to initialise certain room variables).
Bug fixed whereby a few either/or properties could not be changed in play without spurious run-time problems being produced. (In particular, "now X is transparent" or "now X is opaque" caused problems.)
Bug fixed whereby declaring that the player is a person who happens to be initially somewhere other than in the earliest-created room, or outside the map altogether, would cause programming errors or other strange phenomena at run-time.
Bug fixed where a player attempting to UNLOCK a door which is "locked" but which, unbeknownst to the player, has no matching key, would cause a run-time problem complaining about the lack of a "matching key" property.

Windows app

(Windows only) Added support for Glulx mouse events and hyperlinks to the game tab.
(Windows only) The justification style hint is now supported when running a Glulx game in the game tab. As a result, games using Emily Short's "Glulx Image Centering" will now work when run within the application.

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