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|
(local {: insert : unpack} (require :toast.table))
; math
(fn dec [n]
"Decrement n by 1."
(- n 1))
(fn inc [n]
"Increment n by 1."
(+ n 1))
; checks?
(fn empty? [xs]
"Returns true if the lengthable contains no elements."
(= 0 (length xs)))
(fn nil? [x]
"Returns true if the argument is nil."
(= nil x))
(fn number? [n]
"Returns true if the argument is a number."
(= :number (type n)))
; sequences
(fn drop [n xs]
"Returns a table of all but the first n elements in xs."
(let [out []]
(each [i v (ipairs xs)]
(when (> i n) (insert out v)))
out))
(fn first [xs]
"The first element in a sequential table."
(. xs 1))
(fn last [xs]
"The last element in a sequential table."
(. xs (length xs)))
(fn group [n xs]
"Group elements in xs in groups of n.
Extra elements at the end will sit in the final group.
For example, (group 2 [1 2 3 4 5]) results in [[1 2] [3 4] [5]].
One exception is if xs is empty, in which case an empty collection is returned."
(if (empty? xs)
[]
(let [ll #(length (last $))
donext #(= (ll $) n)]
(accumulate [out [[]]
_ v (ipairs xs)]
(do (when (donext out)
(insert out []))
(insert (last out) v
out))))))
; HOF
(fn assoc [?t ...]
"Sets the key `k` in table `t` to the value `v`.
Accepts an arbitrary amount of `k` and `v` pairs.
Returns the mutated table `t`."
(let [t (or ?t {})
lt (inc (length t)) ; for numerical keys
[k v & xs] [...]]
(case k
nil nil
(where k (and (number? k) (> lt k))) (set (. t k) v)
(where k (and (number? k) (= k lt))) (table.insert t v)
_ (tset t k v))
(case (length xs)
0 t
1 (error "assoc expects even number of arguments after table, found odd number")
_ (assoc t (unpack xs)))))
(fn map [f xs]
"Returns a sequential table consisting of the result of apply f to every item in xs."
(accumulate [out []
_ v (ipairs (or xs []))]
(let [mapped (f v)]
(insert out (if (= 0 (select :# mapped))
nil
mapped)))))
{;math
: dec
: inc
; checks?
: empty?
: nil?
: number?
; sequences
: drop
: first
: last
: group
; HOF
: assoc
: map}
|
