s-p-k / greed

A collection of Scheme utilities

Description

greed is a collection of Scheme utilities split to three parts:

• list-utils - a collection of utilities to manipulate Scheme list.
• resistors - a collection of utilities that extracts information form the resistor color code.
• misc - everything else that doesn't fit elsewhere.

greed is written with chicken Scheme implementation in mind. Current version of greed is v0.1.

Loading greed

Loading greed to your Scheme interpreter is as simple as:

(load "/path/to/greed.scm")

If loading was succesfull, you should see something like this:

; loading greed.scm ...
; loading misc.scm ...
; misc loaded successfully.
;; loading list-utils.scm ...
; list-utils loaded successfully.
; loading resistors.scm ...
; resistors loaded successfully.
; greed-v0.1 loaded successfully.
; See LICENSE file for details

What's in list-utils.scm

Here's the list with all the utilities:

• append-element
• exists-in?
• insert
• last
• list-sublists
• negative-car?
• neg-in-list?
• not-atom?
• nth
• positive-car?
• prepend-element
• random-element
• sublist?
• swap-pair

Usage examples for list-utils

• append-element: accepts as input an element and a list and adds that element to the end of the list. Usage example:

  (append-element 3 (list 0 1 2))
  (0 1 2 3) ; output

• exists-in?: takes as input an element and a list. Checks if element exists in list. Usage examples:

  (exists-in? 3 (list 12 3 4))
  #t ; output

  (exists-in? 'a (list 12 3 4))
  #f ; output

• insert: inserts an element to a list to the given position. Usage example:

; This adds number 4 as the third element of the list indexing starts from 1.
(insert (list 1 2 7 8 0 9) 3 4)
(1 2 7 4 8 0 9) ; output.

• last: return the last element of a list. Usage examples:

  (last (list 1 2 23 7 'a 'b 'c))
  c ; output

• list-sublists: if the given list is a list of lists, print the sublists. Usage examples:

  (list-sublists (list 2 3 (list 2 4)))
  ((2 4)) ; output

  (list-sublists (list 2 3 (list 2 4) (list '1 'a 'c)))
  (2 4) ; output
  (1 a c) ; output

• negative-car?: check if the car of a list is negative. Usage example:

  (negative-car? (list 1 2))
  #f ; output

  (negative-car? (list -1 2))
  #t ; output

• not-atom?: returns true if item passed to not-atom? isn't an atom. Usage examples:

  (not-atom? (list 1 2 3))
  #t ; output

  (not-atom? '())
  #f ; output

• nth: returns the nth item of a list. Indexing from 1. If nth element doesn't exist, returns nil. Usage examples:

  (nth 3 (list 1 2 2389))
  2389 ; output

  (nth 3 (list 1 2))
  nil ; output

• positive-car?: works the same way negative-car? does. It just returns true if car of given list is positive, false otherwise. Usage examples:

  (positive-car? (list -1 2 3))
  #f ; output

  (positive-car? (list 1 2 3))
  #t ; output

• prepend-element: adds element to the beginning of a list. Usage examples:

  (prepend-element (list -2 -3 0) -1)
  (-1 -2 -3 0) ; output

• random-element: get a random element from a list. It uses chicken's random. Usage examples:

  (random-element (list 1 2 23 3))
  3 ; output

  (random-element (list 1 2 23 3))
  1 ; output

• sublist?: checks if there's a sublist in the given list. Usage examples:

  (sublist? (list (list 1 3 4 5) 34 3241 -1 34))
  #t ; output

  (sublist? (list 1 2 3))
  #f ; output

  (sublist? (cons 1 2))
  please enter a list ; output

• swap-pair: takes as input a pair, returns the pair with items swaped. Usage examples:

  (swap-pair (cons '1 'a))
  (a . 1) ; output

What's in misc.

misc currently has available only one procedure (the helping procedure is not counted) that computes the sum of the elements of the geometric progression 1, 2, 4, 8, ...

Usage example for geometric-series:

; adds the first five elements of the progression starting from 1.
(geometric-series 5 1)
31 ; output

What's in resistors.scm

• colors-to-resistance: takes as input a list of colors, and returns resistance information.

How to use resistors.scm

Converting resistor color code to information that humans can understand, all the user has to do is something like:

  (colors-to-resistance (list "red" "blk" "red" "red"))
  2000 Ohm, tolerance: 2% ; output

(colors-to-resistance (list "red" "blk" "red"))
2000 Ohm, tolerance: 20% ; output

Known bugs

• list-utils: list-sublist has a different output if there's only one sublist.

• colors-to-resistance: Doesn't make sure that all colors are acceptable.

Please report any bug at mr.dwts gmail com