Javran

import Data.List

twoWay :: Int -> [Int]
twoWay x = [x-1,x+1]

toPascalLine m = map length $ groupDup $ sort m

-- group duplicate elements together
groupDup xs = groupDupAux xs [] []
    where

Javran

#lang racket

(define (my-map f . lists)
  (define (map-intern f xs)
    (if (null? xs)
      '()
      (cons (f (car xs))
            (map-intern f (cdr xs)))))
  (if (ormap null? lists)
    '()

Javran

import Control.Monad

newtype Reader e a = Reader
    { runReader :: e -> a }

instance Monad (Reader e) where
    return x = Reader $ const x
    m >>= f = Reader $ \e ->
        runReader (f (runReader m e)) e

Javran

import Data.Numbers.Primes

seq1 = filter (not . isPrime) [2..]

-- faster
seq2 = seq2Aux primes [2..]
    where
        seq2Aux curP@(p:ps) curX@(x:xs)
            | p  < x = seq2Aux ps curX
            | p  > x = x: seq2Aux curP xs

Javran

我每天都在黑些啥

2014-02-04

• 宇宙大神
• gnome
• ocaml
• R
• SICP section 4.1.6
• "In order to understand recursion, one must first understand recursion."

Javran

(global-set-key (kbd "M-x") 'smex)
(global-set-key (kbd "M-X") 'smex-major-mode-commands) 

Javran

(defun run-scheme-according-to-its-type ()
  "doc todo"
  (interactive)
  (if (racket-file-p (buffer-file-name))
      (progn
        ;; racket file
        (run-racket-with-related-file)
        (other-window 1)
        (end-of-buffer)
        (other-window 1))

Javran

-- if f x then Just x else Nothing

ap (<$) . (guard .)
  :: (Functor f, MonadPlus f) => (a -> Bool) -> a -> f a

Javran

• semantic editor combinators
• The dreaded monomorphism restriction

Javran

(defun pandoc-markdown-to-html (file-src file-dst)
  "convert markdown files into HTML files."
  (shell-command
   (format "pandoc %s -o %s" file-src file-dst)))

(defun current-markdown-html-preview ()
  "generate HTML file for current editing file
using pandoc, and the open browser to preview
the resulting HTML file"
  (interactive)