Types Reference

Relanote uses static typing with Hindley-Milner type inference.

Primitive Types

Type	Description	Example
Unit	No value	()
Bool	Boolean	true, false
Int	Integer	42
Float	Floating point	3.14
String	Text	"hello"

Music Types

Type	Description	Example
Interval	Musical interval	P5, M3, m7
Scale	Collection of intervals	scale { R, M2, M3... }
Chord	Simultaneous intervals	chord [ R, M3, P5 ]
Block	Sequence of notes	| <1> <2> <3> |
Part	Instrument track	part "Piano" [...]
Section	Song section	section "Verse" ...
Song	Complete composition	render ...

Synth Types

Type	Description	Example
Synth	Synthesizer definition	synth Lead = {...}
Oscillator	Waveform type	Sine, Square, Saw
Filter	Filter type	LowPass(1000, 0.5)
Envelope	ADSR envelope	{ A: 0.01, D: 0.1, S: 0.7, R: 0.2 }

Compound Types

Arrays

[1, 2, 3]           ; [Int]
["a", "b", "c"]     ; [String]
[R, M3, P5]         ; [Interval]

Functions

Int -> Int              ; Function from Int to Int
(Int, Int) -> Int       ; Function with two Int parameters
Block -> Block          ; Block transformation

Tuples

(Int, String)           ; Pair of Int and String
(Interval, Interval)    ; Pair of intervals

Type Inference

Types are inferred automatically:

let x = 42              ; x: Int
let s = "hello"         ; s: String
let i = P5              ; i: Interval
let f = \n -> n + 1     ; f: Int -> Int

Type Annotations

Explicit annotations are optional but sometimes helpful:

let x: Int = 42
let transpose: Interval -> Block -> Block = ...

Type Errors

The type checker catches errors at compile time:

; Error: cannot add Scale to Interval
let wrong = Major + P5

; Error: type mismatch
let also_wrong: Int = "hello"

; Error: cannot apply Scale to Int
Major |> 42

Type Classes (Traits)

Some operations work on multiple types:

Eq (Equality)

P5 == P5    ; true
M3 != m3    ; true

Add

; Intervals can be added
P5 + M3     ; M7

; Blocks can be concatenated
| <1> | ++ | <2> |   ; | <1> <2> |

Show

All values can be displayed:

; In the REPL or debug output
P5          ; "P5 (7 semitones)"
Major       ; "Scale { R, M2, M3, P4, P5, M6, M7 }"

Generic Functions

Some built-in functions are generic:

; map works on any Block content
map: (a -> b) -> [a] -> [b]

; repeat works on any Block
repeat: Int -> Block -> Block