Dialog

Dialog is a domain-specific language for creating works of interactive fiction. It is heavily inspired by Inform 7 (Graham Nelson et al. 2006) and Prolog (Alain Colmerauer et al. 1972).

An optimizing compiler, dialogc, translates high-level Dialog code into Z-code, a platform-independent runtime format originally created by Infocom in 1979. Since Dialog version 0d/01, there's also an interactive debugger.

The main discussion is happening in this forum thread.

Manual

The Dialog Manual will tell you everything.

Download

The release archive includes:

  • Full source code for the Dialog compiler.
  • Pre-built executable files for Linux (i386 and x86_64) and Windows.
  • The latest version of the Dialog standard library, and the standard debugging extension.
  • A copy of the manual.

The compiler is distributed under a 2-clause BSD license.

IFID Generator

For reasons outlined in the Treaty of Babel, the Dialog compiler may bug you about declaring a story-specific IFID. To generate the required declaration, simply click the button below.

Notable works

This is what Cloak of Darkness looks like in Dialog.

My IFComp 2018 game Tethered is the first published Dialog game.

Posted Thursday 22-Nov-2018 22:18

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Anonymous
Tue 11-Dec-2018 18:44
if I have an object in a closed transparent container how do I override the default 'you can't reach obj' take fail message?

(instead of [take *]) doesn't seem to work in this case (scope?)
lft
Linus Åkesson
Wed 12-Dec-2018 10:35
if I have an object in a closed transparent container how do I override the default 'you can't reach obj' take fail message?

(instead of [take *]) doesn't seem to work in this case (scope?)

The "can't reach" message is printed by (refuse $), which is invoked before instead-of. So you can override refuse with a negated rule:

~(refuse [take *]) %% Don't refuse to take this object.
Anonymous
Thu 13-Dec-2018 12:55
Is it possible to suppress implicit actions temporarily.
For example
1.dropping something in a held container first tries to take the object before dropping.

2. putting something into something where the first something is in a held container tries to take before putting in

If I know that the take will always succeed can I suppress the first trying to take reporting.
lft
Linus Åkesson
Thu 13-Dec-2018 23:54
If I know that the take will always succeed can I suppress the first trying to take reporting.

Yes, there are several ways. You can override the before-predicate for that particular case, with a negative rule. For each particular action:

~(before [drop $X])
        ($X is #in $Y)
        ($Y is #heldby $Z)
        (current player $Z)

But many actions invoke a common predicate, '(ensure $ is held)', and you can add a new rule to that one instead:

(ensure $X is held)
        ($X is #in $Y)
        ($Y is #heldby $Z)
        (current player $Z)

When the given conditions are true, your rule will succeed, and this prevents the later rule definition in the library from executing.
Eleas
Björn Paulsen
Fri 14-Dec-2018 12:30
The Cloak of Darkness example seems bugged under 0.15. Attempting to go somewhere yields a crash:

fatal error: attempting to store to nonexistent local variable 3:
routine has 0 (pc = 0x2aba)
Eleas
Björn Paulsen
Fri 14-Dec-2018 12:34

Eleas wrote:

The Cloak of Darkness example seems bugged under 0.15. Attempting to go somewhere yields a crash:

fatal error: attempting to store to nonexistent local variable 3:
routine has 0 (pc = 0x2aba)

This is odd. I get the same error when running the first example in chapter 5. I'm running the win32 version of dialogc on Windows 10, in case that matters.
Eleas
Björn Paulsen
Fri 14-Dec-2018 12:44
I've now checked each release of the compiler, and found that moving between rooms only works under release 0b/01. Later than that leads to the fatal error described above.
Anonymous
Fri 14-Dec-2018 13:18

Eleas wrote:

I've now checked each release of the compiler, and found that moving between rooms only works under release 0b/01. Later than that leads to the fatal error described above.

Not sure if it's related but I only get the error when using Gargoyle. Frotz doesn't give the error. (latest versions Windows 10)
Eleas
Björn Paulsen
Fri 14-Dec-2018 13:54
Not sure if it's related but I only get the error when using Gargoyle. Frotz doesn't give the error. (latest versions Windows 10)

Thank you. Can verify. Does anyone know the best way to pass a bug report to one of the maintainers?
lft
Linus Åkesson
Fri 14-Dec-2018 14:47
This looks like a Dialog bug. Thanks for reporting; I'm on it!
lft
Linus Åkesson
Fri 14-Dec-2018 15:36
Fixed in 0c/04.
Anonymous
Tue 18-Dec-2018 13:05
Can I reference an object variable from within the scoring options?
(increase score by (#object variable))
lft
Linus Åkesson
Tue 18-Dec-2018 14:14
Can I reference an object variable from within the scoring options?
(increase score by (#object variable))

As a general rule, queries can't be nested; they don't even have return values.

(Confusingly, rule heads may contain nested expressions, but that is a special case of syntactic sugar.)

But output can be communicated using ordinary parameters. To take the output from one query, and use it as input in another, you would write the queries one after the other. Then you'd use a variable to carry the value.

Assuming you have a predicate ($ has score $) that assigns a score to every object:

        (#object has score $X) %% Here, $X becomes bound (i.e. to the output).
        (increase score by $X) %% Use the value of $X as input.
mstram
Sun 3-Feb-2019 08:01
The following code crashes the compiler

If I substitute the (else) with (if), I get a more reasonable message : "Error (if) without (then).

** The comment editor seems to strip away the indentation ... does it accept some kind of 'markup' ? (I.e. the second line (else) *was* indented.

Also I had much more in the source file, I isolated the crash down to these two lines.

Assertion failed!

Program: c:\bats\dialogc.exe
File: backend_z.c, Line 3348

Expression: call_lab

--------------------
(story title)
(else)
mstram
Sun 3-Feb-2019 08:15
The actual 'realistic' use case for the above was that I had accidentally "not-escaped" the title i.e.
(story title) ( Else) test file
instead of

(story title) \(Else \) test file
lft
Linus Åkesson
Sun 3-Feb-2019 08:54
Thanks! I'll fix that.

There's currently no tag to retain formatting in the comments; sorry for that. I've been using hardspaces to get around it. I suppose I'll fix that too.
mstram
Sun 3-Feb-2019 09:39
Are global flags (or maybe it's the (now) predicate) designed to work in "open code" (like global variables?

If I put :

(now)(a-global-flag) in "open code", I get :

"Special syntax cannot be redefined"

Mike
lft
Linus Åkesson
Sun 3-Feb-2019 21:54

mstram wrote:

Are global flags (or maybe it's the (now) predicate) designed to work in "open code" (like global variables?

If I put :

(now)(a-global-flag) in "open code", I get :

"Special syntax cannot be redefined"

Mike

Anything that starts in the very first column of a line is interpreted as a rule definition, so the compiler thinks you're trying to define a rule for a predicate called '(now)'. But that's special syntax, so its behaviour can't be modified.

If you would like the global flag to be initially set, define a rule with an empty rule body:

(a-global-flag)

This is analogous to how the initial values of other kinds of dynamic properties are defined. For instance:

(#box is #heldby #player)
(#box is open)
(current player #player)
mstram
Mon 4-Feb-2019 00:24
Ok, thanks, that works ... but ...

The "first-column-global" (fcg ? :)) is not showing up in the debugger's @dynamic output.

The flag *does* work though (of course),if I enter
(a-global-flag), giving the expected "Query succeeded:(a-global-flag)

The @dy(namic) cmd seems to be only finding global flags that are referenced inside a rule :

(test)
__ (now)(a-global-flag)


Mike
lft
Linus Åkesson
Mon 4-Feb-2019 15:02

mstram wrote:

The @dy(namic) cmd seems to be only finding global flags that are referenced inside a rule

That is correct. A predicate is only considered dynamic if it appears in a (now)-statement somewhere. So, if there's a (now) (a-global-flag) somewhere, then (a-global-flag) is regarded as a boolean variable that can be toggled at runtime. And its initial value is determined by the rule definitions for it. Otherwise, it behaves more like a boolean-valued function, and the rule definitions make up its function body.

It's a matter of terminology. Something that can change is dynamic, but something that cannot possibly change is not.
mstram
Wed 6-Feb-2019 11:12
This crashes both the windows and linux-64 compilers, version
0d02_0_19, and 0e01_0_20,but NOT the 0c05_0_17 version

#gnue
(name *) gnue
(dict *) plane
(vehicle *)


Again it's only a code fragment, but I was trying to split a larger program into multiple files.

Mike
lft
Linus Åkesson
Wed 6-Feb-2019 20:10
Thank you! I can reproduce it. Amusingly, I can get the program to compile by adding a room:

(room #x)

But it's still a compiler bug, of course, and I'll fix it as soon as possible.
lft
Linus Åkesson
Wed 13-Feb-2019 22:01
Fixed in 0e/02.