Functions

Relanote is a pure functional language. Functions are first-class values that can be passed around, composed, and applied to data.

Lambda Expressions

Create anonymous functions with the \ (lambda) syntax:

; Single parameter
\x -> x + P8

; Multiple parameters
\x y -> x ++ y

; Used inline
| <1> <2> <3> | |> (\b -> b |> repeat 2)

Let Bindings

Use let to bind values and create named functions:

scale Major = { R, M2, M3, P4, P5, M6, M7 }

; Bind a value
let melody = | <1> <3> <5> |

; Bind a function
let up_octave = \b -> b |> transpose P8

; Apply
melody |> up_octave

Let-In Expressions

For local bindings within an expression:

scale Major = { R, M2, M3, P4, P5, M6, M7 }

let result =
  let theme = | <1> <3> <5> | in
  let variation = theme |> reverse in
  theme ++ variation

result

Built-in Functions

Block Transformations

Function	Description	Example
reverse	Reverse slot order	melody |> reverse
repeat n	Repeat n times	melody |> repeat 2
transpose interval	Shift all pitches	melody |> transpose P5

scale Major = { R, M2, M3, P4, P5, M6, M7 }

let theme = | <1> <2> <3> <4> |

; Transformations
let reversed = theme |> reverse
let doubled = theme |> repeat 2
let higher = theme |> transpose P5

Rhythm & Feel

Function	Description	Example
swing	Apply swing feel	melody |> swing
double_time	Halve durations	melody |> double_time

scale Major = { R, M2, M3, P4, P5, M6, M7 }

let straight = | <1> <2> <3> <4> <5> <6> <7> <8> |

; Jazz swing feel
let swung = straight |> swing

; Double tempo
let fast = straight |> double_time

Effects

Function	Description	Example
volume level	Set volume (0.0-1.0)	melody |> volume 0.8
reverb level	Add reverb	melody |> reverb 0.5
room_reverb	Room reverb preset	melody |> room_reverb
hall_reverb	Hall reverb preset	melody |> hall_reverb
plate_reverb	Plate reverb preset	melody |> plate_reverb
dry	No reverb	melody |> dry

scale Major = { R, M2, M3, P4, P5, M6, M7 }

let melody = | <1> <3> <5> <8> |

; Apply effects
melody
  |> hall_reverb
  |> volume 0.7

Utility

Function	Description	Example
metronome bars beats	Generate click track	metronome 4 4

; 4 bars of 4/4 metronome
let click = metronome 4 4 |> volume 0.3

Function Composition

Compose functions with >>:

scale Major = { R, M2, M3, P4, P5, M6, M7 }

; Create a reusable transformation
let jazz_transform = transpose P5 >> swing >> room_reverb

; Apply to any melody
let melody1 = | <1> <3> <5> |
let melody2 = | <5> <4> <3> <2> |

melody1 |> jazz_transform
melody2 |> jazz_transform

Higher-Order Functions

Functions that take or return other functions:

scale Major = { R, M2, M3, P4, P5, M6, M7 }

; Function that returns a transposition function
let make_transposer = \interval -> (\b -> b |> transpose interval)

let up_fifth = make_transposer P5
let up_octave = make_transposer P8

| <1> <3> <5> | |> up_fifth
| <1> <3> <5> | |> up_octave

Practical Example: Theme and Variations

scale Major = { R, M2, M3, P4, P5, M6, M7 }

; Original theme
let theme = | <1> <3> <5> <3> <1>~ - - - |

; Variation functions
let retrograde = \b -> b |> reverse
let inversion = \b -> b |> transpose P8 |> reverse
let augmentation = \b -> b |> repeat 2
let diminution = \b -> b |> double_time

; Apply variations
let var1 = theme |> retrograde
let var2 = theme |> inversion
let var3 = theme |> augmentation
let var4 = theme |> diminution

; Combine all
theme ++ var1 ++ var2 ++ var3 ++ var4

Best Practices

1. Name transformations: Give meaningful names to composed functions
2. Keep functions pure: No side effects, same input = same output
3. Compose small functions: Build complex behavior from simple pieces
4. Use partial application: transpose P5 creates a reusable function
5. Document with comments: Use ; to explain complex transformations