Patterns are opaque. P a is a pattern with elements of type a. Patterns are constructed, manipulated and destructured using the functions provided, ie. the pattern instances for return, pure and toList, and the pattern specific functions undecided and toP.

F.toList (toP [1,2,3] * 2) == [2,4,6]

Patterns are Functors. fmap applies a function to each element of a pattern.

fmap (* 2) (toP [1,2,3,4,5]) == toP [2,4,6,8,10]

Patterns are Monoids. mempty is the empty pattern, and mappend (<>) makes a sequence of two patterns.

1 <> mempty <> 2 == toP [1,2]

Patterns are Applicative. The pattern instance is pointwise & truncating, as for ZipList. pure lifts a value into an infinite pattern of itself, <*> applies a pattern of functions to a pattern of values. This is distinct from the combinatorial instance for ordinary lists, ie. where pure is return and <*> is ap.

liftA2 (+) (toP [1,2]) (toP [3,4,5]) == toP [4,6]
liftA2 (+) [1,2] [3,4,5] == [4,5,6,5,6,7]

Patterns are Monads, and therefore allow do notation.

let p = do {x <- toP [1,2]; y <- toP [3,4,5]; return (x,y)}
in p == toP [(1,3),(1,4),(1,5),(2,3),(2,4),(2,5)]

Patterns are Numerical. The instances can be derived from the Applicative instance.

1 + toP [2,3,4] == liftA2 (+) 1 (toP [2,3,4])

Lift a value to a pattern deferring deciding if the constructor ought to be pure or return to the consuming function. The pattern instances for fromInteger and fromRational make undecided patterns. In general horizontal functions (ie. <>) resolve using return and vertical functions (ie. zip) resolve using pure. In the documentation functions that resolve using pure are annotated as implicitly repeating.

1 <> toP [2,3] == return 1 <> toP [2,3]
toP [1,2] * 3  == toP [1,2] * pure 3

The basic list to pattern function, inverse is unP.

unP (toP "str") == "str"

There is a default sound, given by defaultSynthdef from Sound.SC3.

audition defaultSynthdef

If no instrument is specified we hear the default.

audition (pbind [(K_degree,pxrand 'α' [0,1,5,7] inf)
                ,(K_dur,toP [0.1,0.2,0.1])])

> Pbind(\degree,(Pxrand([0,1,5,7],inf))
>      ,\dur,Pseq([0.1,0.2,0.1],1)).play

The pattern above is finite, toP can sometimes be replaced with pseq.

audition (pbind [(K_degree,pxrand 'α' [0,1,5,7] inf)
                ,(K_dur,pseq [0.1,0.2,0.1] inf)])

Type specialised toList. undecided values are singular.

F.toList (undecided 'a') == ['a']
unP (return 'a') == ['a']
"aaa" `L.isPrefixOf` unP (pure 'a')

Variant of unP where undecided values are repeated.

unP_repeat (return 'a') == ['a']
take 2 (unP_repeat (undecided 'a')) == ['a','a']
take 2 (unP_repeat (pure 'a')) == ['a','a']

Lift unary list function to pattern function.

Lift binary list function to pattern function.

liftP2 (zipWith (+)) (toP [1,2]) (toP [3,4,5]) == toP [4,6]
liftA2 (+) (toP [1,2]) (toP [3,4,5]) == toP [4,6]

Lift binary list function to implicitly repeating pattern function.

Lift ternary list function to pattern function.

Lift ternary list function to implicitly repeating pattern function.

An implicitly repeating pattern variant of zipWith.

zipWith (*) [1,2,3] [5,6] == [5,12]
pzipWith (*) (toP [1,2,3]) (toP [5,6]) == toP [5,12]

It is the basis for lifting binary operators to patterns.

toP [1,2,3] * toP [5,6] == toP [5,12]

let p = pzipWith (,) (pseq [1,2] 2) (pseq [3,4] inf)
in p == toP [(1,3),(2,4),(1,3),(2,4)]

zipWith (,) (return 0) (return 1) == return (0,1)
pzipWith (,) 0 1 == undecided (0,1)

An implicitly repeating pattern variant of zipWith3.

An implicitly repeating pattern variant of zip.

zip (return 0) (return 1) == return (0,1)
pzip (undecided 3) (undecided 4) == undecided (3,4)
pzip 0 1 == undecided (0,1)

Note that pzip is otherwise like haskell zip, ie. truncating.

zip [1,2] [0] == [(1,0)]
pzip (toP [1,2]) (return 0) == toP [(1,0)]
pzip (toP [1,2]) (pure 0) == toP [(1,0),(2,0)]
pzip (toP [1,2]) 0 == toP [(1,0),(2,0)]

Pattern variant of zip3.

Pattern variant on unzip.

let p = punzip (pzip (toP [1,2,3]) (toP [4,5]))
in p == (toP [1,2],toP [4,5])