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View FunctionalTV problem 476: num-digits
How many digits?
Imagine you took all the integers between n and m (exclusive, n <
m) and concatenated them together. How many digits would you have?
Write a function that takes two numbers and returns how many
digits. Note that the numbers can get very big, so it is not
possible to build the string in the general case.
View gist:30894e53da19d712021906629cf1583c
(defn frequencies-by
"Returns a map from distinct results of (f item) in coll
to a vector duple of all (k item) (if k is provided, or items otherwise)
with the same (f item) value, and the number of times (f item) appears.
([f coll]
(frequencies-by f nil coll))
([f k coll]
(persistent! ;; copied from clojure.core
View gist:679561f6da86863316499fe134c31dd7
(defn slow-assoc [m & [k v & kvs :as dat]]
(if (empty? dat)
(apply slow-assoc (assoc m k v) kvs)))
(defn emit-assoc [ [ksym vsym]]
`(assoc ~ksym ~vsym))
(defmacro fast-assoc [msym & kvsyms]
(let [assocs (map #(emit-assoc %)
View Composable Rules
(defn monoid* [init body]
`(fn f#
(fn [& ~'xs] ~init))
(fn [& ~'xs] (~body (apply ~'r ~'xs))))
([~'r1 ~'r2]
(fn [& ~'xs] (~body(apply ~'r1 ~'xs) (apply ~'r2 ~'xs))))
([~'r1 ~'r2 & ~'rs]
(fn [& ~'xs]
KingCode / gist:8970fe4e2308127ba467ac7f57d3f78b
Created Oct 16, 2020
Hand rolled sequence to prevent chunking
View gist:8970fe4e2308127ba467ac7f57d3f78b
(defn lazify [[x & xs :as coll]]
(when (seq coll)
(cons x (lazify xs)))))
(def my-lazy-input (lazify [1 2 4 1 2 3 1]))
(type my-lazy-input) ;; => clojure.lang.LazySeq
(type (rest my-lazy-input)) ;; => clojure.lang.LazySeq
;; So my-lazy-input is truly lazy all the wal...Now I want to feed it to 'sequence
KingCode / my-ns-test.clj
Last active Jul 1, 2020
Properties test for Functional-TV challenge #384
View my-ns-test.clj
;; see
(ns my-ns-test
(:require [my-ns :as sut]
[ :as prop]
[clojure.test.check.generators :as gen]
[clojure.test.check.clojure-test :refer [defspec]]))
(let [alias-str "sut"
sym (symbol (str alias-str "/parallel?"))]
KingCode / gist:773560f4ab5bf91e660a2a26e581b036
Last active Nov 2, 2020
cond-let and cond-let> macros, to leverage bindings between test and result expressions, as well as earlier ones (for cond-let)
View gist:773560f4ab5bf91e660a2a26e581b036
(ns cond-let)
;; (cond-let
;; (odd? x) [x n] (inc x)
;; (< n 10) [y (inc n)] 10
;; :else n))
;; we want the above to yield
;; (let [x n]
;; (if (odd? x)
;; (inc x)
KingCode / gist:a954ced2aeaa22f34332fc81f75f9969
Last active Oct 27, 2018
Scoping transducer for pipelining sub-structures without losing the container.
View gist:a954ced2aeaa22f34332fc81f75f9969
(require '[clojure.core.async :as async :refer [chan <!! put!]])
(defn save-to [c save-f]
(fn [rf]
([] (rf))
([acc] (rf acc))
([acc x]
(put! c (save-f x))
(rf acc x)))))
KingCode / transducer.clj
Last active Oct 1, 2018
An implemementation of the transducer API from scratch, as a learning aid.
View transducer.clj
(ns scratch.transducer
(:refer-clojure :exclude [comp map filter mapcat take drop
take-while drop-while
;; sequence
View gist:ef2ac029dbcf2881ad1762611f837d56
(ns hellospec.fizzbuzz
(:require [clojure.spec :as s]
[clojure.spec.test :as stest]
;; to accomodate KLIPSE:
;; "[...]cljs.spec.gen.frequency is undefined[...]"
#?(:clj [clojure.spec.gen :as gen]
:cljs [clojure.test.check.generators :as gen])))
;; A fizzbuzz which doesn't use condition checking/branching
(defn fizzbuzz