RosettaCodeData/Task/Lah-numbers/J/lah-numbers.j
2023-07-01 13:44:08 -04:00

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NB. use: k lah n
lah=: ! :(!&<: * %&!~)&x: NB. `%~' is shorter than `*inv'
NB. wory_lah translates lah to algebraic English.
Monad =: :[: NB. permit only a y argument
Dyad =: [: : NB. require x and y arguments
but_1st =: &
decrement =: <: Monad
NB. ! means either factorial or combinations (just as - means negate or subtract)
factorial =: ! Monad
combinations =: ! Dyad
into =: *inv Dyad
times =: * Dyad
extend_precision =: x: Monad
wordy_lah =: ((combinations but_1st decrement) times (into but_1st factorial))but_1st extend_precision Dyad