Difference between revisions of "Expression"

Latest revision as of 18:46, 27 January 2023

An Expression is a representation of a value that is resolved while the deck is playing. Some common uses for expressions include: Reading the value of variables, performing simple math, or creating randomness. Expressions can also be nested and combined to support more complex things, such as calculating health for characters, crafting procedural games and animations, and even making generative artwork.

Expressions always resolve to a numeric value.

Some expressions take arguments. For example, when reading the value of a Variable, you need to specify which variable to read. When adding two numbers, you need to specify which two numbers (or expressions) to add. Other expressions don't take any arguments, such as the Time elapsed since the card started.

Using Expressions

A screenshot of a Rule response where the "beaker" button for editing the expression is circled with red highlighter

Press the beaker button (circled here in red) to use an expression.

Expressions are an important component of Rules in Castle. Typically, when editing a rule, any numeric value can be an expression. To edit an expression, look for the round beaker icon to the left of a number input. Press it to open a sheet to edit that expression.

List of Expression Types

Some expressions are contextual to the enclosing Response. For example, the "Number of repeats finished" expression only appears if already inside a Repeat response.

Values

A constant number. This is the same as not using an expression.
The value of a variable
The value of a Behavior property

Choices

Weighted choose
Choose
Maximum
Minimum

Randomness

A random number with a Gaussian distribution
Perlin noise in 2 dimensions
A random number in a range

Spatial relationships

The Y coordinate of the user's touch
The X coordinate of the user's touch
The speed of an actor
The angle of motion of an actor
The angle from one actor to another (degrees)
The distance between two actors

Arithmetic

The number of Repeats finished
Logarithm
Power
Modulo
Divide
Multiply
Subtract
Add

Clock

Time elapsed since the card started
The clock tempo
Time since the last beat
The current bar
The current beat in the current bar
Beats elapsed since the card started

Music

The note played (only appears under the "track plays note" trigger)

Functions

The number of actors with a Tag
Smooth
Degrees to radians
Sine
Clamp a value between two bounds
Mix two values
Round
Round down
Absolute value

Sensors

Device Tilt X
Device Tilt Y

@@ Line 1: / Line 1: @@
-Expressions in Castle are used for many things, including calculating health for characters, crafting procedural games and animations, and even making generative artwork. Expressions sometimes take in some values as arguments and always return a result value.
+An '''Expression''' is a representation of a value that is resolved while the deck is playing. Some common uses for expressions include: Reading the value of variables, performing simple math, or creating randomness. Expressions can also be nested and combined to support more complex things, such as calculating health for characters, crafting procedural games and animations, and even making generative artwork.
+Expressions always resolve to a numeric value.
+Some expressions take arguments. For example, when reading the value of a [[Variable]], you need to specify which variable to read. When adding two numbers, you need to specify which two numbers (or expressions) to add. Other expressions don't take any arguments, such as the '''Time elapsed since the card started'''.
+== Using Expressions ==
+[[File:Expression-beaker-button.jpg|alt=A screenshot of a Rule response where the "beaker" button for editing the expression is circled with red highlighter|thumb|Press the beaker button (circled here in red) to use an expression.]]
+Expressions are an important component of [[Rule|Rules]] in Castle. Typically, when editing a rule, any numeric value can be an expression. To edit an expression, look for the round beaker icon to the left of a number input. Press it to open a sheet to edit that expression.
 == List of Expression Types ==
-The following is a list of expression types in the order that they are listed when viewed in the Castle "Choose expression type" sheet
+Some expressions are contextual to the enclosing [[Response]]. For example, the "Number of repeats finished" expression only appears if already inside a [[Repeat]] response.
 === Values ===
-* [[The value of a variable expression|The value of a variable]]
+* A constant number. This is the same as not using an expression.
-*[[A constant number expression|A constant number]]
+*The value of a [[variable]]
+*The value of a [[Behavior]] property
 === Choices===
-* [[Weighted choose expression|Weighted choose]]
+* Weighted choose
-*[[Choose expression|Choose]]
+*Choose
-*[[Maximum expression|Maximum]]
+*Maximum
-*[[Minimum expression|Minimum]]
+*Minimum
 ===Randomness===
@@ Line 20: / Line 29: @@
 *[[A random number with a Gaussian distribution expression|A random number with a Gaussian distribution]]
 *[[Perlin noise in 2 dimensions expression|Perlin noise in 2 dimensions]]
-*[[A random number in a range expression|A random number in a range]]
+*A random number in a range
+===Spatial relationships===
-===Spacial relationships===
+*The Y coordinate of the user's touch
+*The X coordinate of the user's touch
+*The speed of an actor
+*The angle of motion of an actor
+*The angle from one actor to another (degrees)
+*The distance between two actors
+=== Arithmetic ===
-*[[The speed of an actor expression|The speed of an actor]]
+*The number of [[Repeat|Repeats]] finished
-*[[The angle of motion of an actor expression|The angle of motion of an actor]]
+*Logarithm
-*
+*Power
-[[The angle from one actor to another (degrees) expression|The angle from one actor to another (degrees)]]
+* Modulo
-*[[The distance between two actors expression|The distance between two actors]]
+*Divide
+* Multiply
+* Subtract
+* Add
-=== Arithmetic ===
+===[[Clock]]===
-*[[The number of repeats finished expression|The number of repeats finished]]
+*Time elapsed since the card started
-*[[Logarithm expression|Logarithm]]
+* The clock tempo
-*[[Power expression|Power]]
+*Time since the last beat
-* [[Modulo expression|Modulo]]
+* The current bar
-*[[Divide expression|Divide]]
+*The current beat in the current bar
-* [[Multiply expression|Multiply]]
+*Beats elapsed since the card started
-* [[Subtract expression|Subtract]]
-* [[Add expression|Add]]
-===Clock===
+=== [[Music]] ===
-*[[Time elapsed since the card started expression|Time elapsed since the card started]]
+* The note played (only appears under the "track plays note" trigger)
-* [[The clock tempo expression|The clock tempo]]
-*[[Time since the last beat expression|Time since the last beat]]
-* [[The current bar expression|The current bar]]
-*[[The current beat in the current bar expression|The current beat in the current bar]]
-*[[Beats elapsed since the card started expression|Beats elapsed since the card started]]
 === Functions===
-*[[The number of actors with a tag expression|The number of actors with a tag]]
+*The number of actors with a [[Tag]]
-*[[Degrees to radians expression|Degrees to radians]]
+*[[Smooth expression|Smooth]]
-*[[Sine expression|Sine]]
+*Degrees to radians
-*[[Clamp a value between two bounds expression|Clamp a value between two bounds]]
+*Sine
-*[[Mix two values expression|Mix two values]]
+*Clamp a value between two bounds
-*[[Round expression|Round]]
+*Mix two values
-* [[Round down expression|Round down]]
+*Round
-*[[Absolute value expression|Absolute value]]
+* Round down
+*Absolute value
+=== Sensors ===
+* Device [[Tilt]] X
+* Device Tilt Y