Expressions

An expression is anything that gives a value: the right-hand side of a [let], a condition, an argument, or what stands between [ and ] in the middle of a line.

Operators

From the one that binds the loosest to the one that binds the tightest:

Parentheses group: ($a + 1) * 2.

:= start
[let $gold = 12]
[let $rich = $gold > 10 and not ($gold == 13)]
Alice: Half of it is [$gold / 2].
---

Arithmetic works on numbers. An operation between two integers gives an integer, except a division, which always gives a float: 7 / 2 is 3.5. Dividing by zero stops the dialogue with an error.

== and != compare two values of the same type, dicts included.

The types are checked when the file is read wherever they are known: "a" + 1 or [if 3] is reported before the dialogue ever runs. What depends on a variable or on a function is checked when it is evaluated.

has

has asks whether something holds something else. What it means depends on its left-hand side.

On a dict, it tells whether the dict holds a key, whatever the value under it. The key is a bare word, a string or a variable:

:= start
[let $stats = {strength: 12, agility: 0}]
[if $stats has strength]
    Alice: I can lift that.
[if not ($stats has magic)]
    Alice: No spell from me, though.
[let $key = "agility"]
[if $stats has $key]
    Alice: An agility of zero is still an agility.
---

Only the dict itself is searched, not the ones nested in it.

On a string, the question goes to the game: Alice has Angry asks it whether the subject Alice has the feature Angry. What a subject and a feature are is up to the game.

:= start
[if Alice has Angry]
    Alice: Give it back!
[else]
    Alice: Could I have it back?
---

not binds tighter than has: write not ($stats has magic), with the parentheses.

Functions

A function is called by its name followed by its arguments between parentheses, the ( touching the name: max($a, $b). See Commands and functions.