Functions

A function is a block of code that provides a value to your Yarn scripts, which you can use in if statements, or store in variables.

In Yarn Spinner scripts, functions perform two main kinds of task:

• Functions let you get values that change over time, or that depend on other values. For example, the random function returns a different random number every time you call it.

• Functions let you get data from your game back into your scripts.

You call a function inside an expression. For example:

// Inside an if statement:
<<if dice(6) == 6>>
    You rolled a six!
<<endif>>

// Inside a line:
Gambler: My lucky number is {random_range(1,10)}!

Built-In Functions

Yarn Spinner comes with several built-in functions for you to use.

random()

random returns a random number between 0 and 1 each time you call it.

random_range(number a, number b)

random_range returns a random integer between a and b, inclusive.

dice(number sides)

dice returns a random integer between 1 and sides, inclusive.

For example, dice(6) returns a number between 1 and 6, just like rolling a six-sided die.

round(number n)

round rounds n to the nearest integer.

round_places(number n, number places)

round_places rounds n to the nearest number with places decimal points.

floor(number n)

floor rounds n down to the nearest integer, towards negative infinity.

ceil(number n)

ceil rounds n up to the nearest integer, towards positive infinity.

inc(number n)

inc rounds n up to the nearest integer. If n is already an integer, inc returns n+1.

dec(number n)

inc rounds n down to the nearest integer. If n is already an integer, inc returns n-1.

decimal(number n)

decimal returns the decimal portion of n. This will always be a number between 0 and 1. For example, decimal(4.51) will return 0.51.

int(number n)

int rounds n down to the nearest integer, towards zero.

This is different to floor, because floor rounds to negative infinity.

Custom Functions

You can define your own custom functions in Yarn Spinner. For more information, see # Defining Commands and Functions .

Functions are not intended to be a way for you to send instructions to your game. For that purpose, you should use commands.

In particular, functions are not guaranteed to be called in the same order as they appear in your code, or even be called at all if Yarn Spinner believes the result can be cached. As much as possible, custom functions should be pure functions, and have no side effects besides returning a value based on parameters.