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u wut m8

Name: Anonymous 2012-09-22 12:08



$ racket

Welcome to Racket v5.1.3.3

(+)

0

Name: Anonymous 2012-09-22 12:28

http://en.wikipedia.org/wiki/Identity_element

Name: Anonymous 2012-09-22 13:00

(/ (*) (- (*) (*)))

Name: Anonymous 2012-09-22 14:08



(define (a-plus-abs-b a b)

  ((if (> b 0) + -) a b))

Name: Anonymous 2012-09-22 14:46

>>4
Haskell is superior:
a-plus-abs-b = (+ abs)

instance (Num a, Eq a) => Num (x -> a) where

    fromInteger = const . fromInteger

    f + g = liftM2 (+) f g

    f * g = liftM2 (*) f g

    f - g = liftM2 (-) f g

    negate = (negate .)

    abs = (abs .)

    signum = (signum .)

Name: Anonymous 2012-09-22 14:47

>>5
s/-/_/g

Name: Anonymous 2012-09-23 4:23

Fun fact: in the J programming language, (f g) = x f (g y) if f is a binary operator and g is a unary one.

   f =. +|

   _10 f _20

Name: Anonymous 2012-09-23 14:58

>>7
http://wiki.nars2000.org/index.php/Trains
It's the same way in NARS2000 Extended APL (which adopted them from J).

      f←(+|)

      ¯10 f ¯20

It can also be written with the ∘ operator.

      f←+∘|

      ¯10 f ¯20

Name: Anonymous 2012-09-23 15:05

>>1,2
APL arithmetic functions also return the identity element when given an empty vector.

      +/⍳0

0

      -/⍳0

0

      ×/⍳0

1

      ÷/⍳0

1

      */⍳0

1

u wut m8

1 Name: Anonymous 2012-09-22 12:08

2 Name: Anonymous 2012-09-22 12:28

3 Name: Anonymous 2012-09-22 13:00

4 Name: Anonymous 2012-09-22 14:08

5 Name: Anonymous 2012-09-22 14:46

6 Name: Anonymous 2012-09-22 14:47

7 Name: Anonymous 2012-09-23 4:23

8 Name: Anonymous 2012-09-23 14:58

9 Name: Anonymous 2012-09-23 15:05