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;;;; This contains some of the core Hy functions used
;;;; to make functional programming slightly easier.
;;;;
(defn _numeric-check [x]
(if (not (numeric? x))
(raise (TypeError (.format "{0!r} is not a number" x)))))
(defn cycle [coll]
"Yield an infinite repetition of the items in coll"
(setv seen [])
(for [x coll]
(yield x)
(.append seen x))
(while seen
(for [x seen]
(yield x))))
(defn dec [n]
"Decrement n by 1"
(_numeric-check n)
(- n 1))
(defn distinct [coll]
"Return a generator from the original collection with duplicates
removed"
(let [[seen []] [citer (iter coll)]]
(for [val citer]
(if (not_in val seen)
(do
(yield val)
(.append seen val))))))
(defn drop [count coll]
"Drop `count` elements from `coll` and yield back the rest"
(let [[citer (iter coll)]]
(try (for [i (range count)]
(next citer))
(catch [StopIteration]))
citer))
(defn even? [n]
"Return true if n is an even number"
(_numeric-check n)
(= (% n 2) 0))
(defn filter [pred coll]
"Return all elements from `coll` that pass `pred`"
(let [[citer (iter coll)]]
(for [val citer]
(if (pred val)
(yield val)))))
(defn inc [n]
"Increment n by 1"
(_numeric-check n)
(+ n 1))
(defn instance? [klass x]
(isinstance x klass))
(defn iterable? [x]
"Return true if x is iterable"
(try (do (iter x) true)
(catch [Exception] false)))
(defn iterate [f x]
(setv val x)
(while true
(yield val)
(setv val (f val))))
(defn iterator? [x]
"Return true if x is an iterator"
(try (= x (iter x))
(catch [TypeError] false)))
(defn neg? [n]
"Return true if n is < 0"
(_numeric-check n)
(< n 0))
(defn none? [x]
"Return true if x is None"
(is x None))
(defn numeric? [x]
(import numbers)
(instance? numbers.Number x))
(defn nth [coll index]
"Return nth item in collection or sequence, counting from 0"
(if (not (neg? index))
(if (iterable? coll)
(try (first (list (take 1 (drop index coll))))
(catch [IndexError] None))
(try (get coll index)
(catch [IndexError] None)))
None))
(defn odd? [n]
"Return true if n is an odd number"
(_numeric-check n)
(= (% n 2) 1))
(defn pos? [n]
"Return true if n is > 0"
(_numeric_check n)
(> n 0))
(defn remove [pred coll]
"Return coll with elements removed that pass `pred`"
(let [[citer (iter coll)]]
(for [val citer]
(if (not (pred val))
(yield val)))))
(defn repeat [x &optional n]
"Yield x forever or optionally n times"
(if (none? n)
(setv dispatch (fn [] (while true (yield x))))
(setv dispatch (fn [] (for [_ (range n)] (yield x)))))
(dispatch))
(defn repeatedly [func]
"Yield result of running func repeatedly"
(while true
(yield (func))))
(defn take [count coll]
"Take `count` elements from `coll`, or the whole set if the total
number of entries in `coll` is less than `count`."
(let [[citer (iter coll)]]
(for [_ (range count)]
(yield (next citer)))))
(defn take-nth [n coll]
"Return every nth member of coll
raises ValueError for (not (pos? n))"
(if (pos? n)
(let [[citer (iter coll)] [skip (dec n)]]
(for [val citer]
(yield val)
(for [_ (range skip)]
(next citer))))
(raise (ValueError "n must be positive"))))
(defn take-while [pred coll]
"Take all elements while `pred` is true"
(let [[citer (iter coll)]]
(for [val citer]
(if (pred val)
(yield val)
(break)))))
(defn zero? [n]
"Return true if n is 0"
(_numeric_check n)
(= n 0))
(def *exports* ["cycle" "dec" "distinct" "drop" "even?" "filter" "inc"
"instance?" "iterable?" "iterate" "iterator?" "neg?"
"none?" "nth" "numeric?" "odd?" "pos?" "remove" "repeat"
"repeatedly" "take" "take_nth" "take_while" "zero?"])
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