Help in Lisp sorting

[coolman]

Does anyone know about LISP Programming

I am trying to make this program where I have 3 types of cars, which are ford bmw merc

ford has focus and fiesta BMW has 1series and 2series and the merc has SK100 and SK200

well basically i am trying to put them in the correct list for example focus will go into ford list and SK100 will go to the merc list

at the moment to store the data i will use defparameter

example

(defparameter *cars* ' ( focus fiesta 1series 2series SK100 SK200))

so now i want to create a funtion where the cars will go into the correct list, so it will sort the cars into an orgranised lisp when I ran the function. so the cars should be in a randam list but when i ran the function it should sort it into the correct list

(test-a-car 2) the 2 means 2 cars pair a list

ford (fiesta focus)
Merc (SK100 SK200)
BMW (1series 2series)

I have done all the searching in the Internet but I cant find nothing I have tried loads of things but i just hate lisp so please guide me somehow

[teknomage1]

Lisp is god's programming language.

You could make an a-list that relates each car to it's manufacturor (Why you would have an exercise relating cars in a language with a primitive called CAR is beyond me). Anyway, an a-list relates data like this (key1 value1 key2 value2 ...) . There's a function for finding the value of a key called GETF. so for this example you could do something like this.

(defparameter *models* '(fiesta ford sk100 merc focus ford))
(getf *models* 'fiesta)
=> FORD
(getf *models* 'sk100)
=> MERC
(getf *models* 'focus)
=>FORD

[coolman]

say i got a list full of ramdam cars and they are jumblbed up but i now wanana create a funtion where it will put them in the correct list

(test-a-car 2)

when ran this function it will automactically display it in organised list so the right car will go in the right and it will display the list like


I want it to display a list
ford (focus fieasta)
Merc (SK100 SK200)

[coolman]

I was thinking of using a loop where i will have type of manfacture is ford(key1) and the car is focus (value1) den i would have another list called ford and that would match with the manfacture ford(key1) and therefore the focus value will go into that new ford list

but the only way i can make dat work is if i use loop but i cant seem to make it work

[teknomage1]

LOOP is a bitch, plain and simple. It's easier to look at this as a MAP problem i believe. MAP is like foreach for list elements and vectors. So assuming you have an a-list like I descibed above that relates models to manufacturers, you could then use MAP to run over a list of manufacturers and use REMOVE-IF-NOT to select only the models of that manufacturer.
REMOVE-IF-NOT takes a predicate function as it's first parameter so that's where we want to test and see if the result of the :key expression is equal to the manufacturer we're looking at. Since there is no built in function to do this and it is too specific to define a new function for, we can use the LAMBDA function to generate a new anonymous function. The :key function is evaluated for each element REMOVE-IF-NOT examines before it goes to the predicate function. In this case we want the manufacturor of the model so we look it up from the a-list.

(defparameter *models* '(fiesta ford sk100 merc focus ford 1series bmw))

(defun order-models (model-list manufacturer-list)
  (map 'list
       (lambda (m)
	 (list m (remove-if-not
		  (lambda (y) (equal y m))
		  model-list
		  :key (lambda (x) (getf *models* x)))))
       manufacturer-list))
(order-models '(fiesta sk100 focus 1series) '(bmw ford merc))
=>
((BMW (1SERIES)) (FORD (FIESTA FOCUS)) (MERC (SK100)))

[coolman]

but i want another defun top of that where i will have (test-a-car 3)

and the 3 means 3 car pair list so if ford has more cars like feasta focus mondeo ka den the output should be

ford (focus fiesta mondeo) den another ford list cos u can only have 3 cars a list ford (ka)

c wat i mean

[teknomage1]

Well the version I gave you is length independent, so why don't you write another function that splits lists which are too long?

[coolman]

Now I want to add a bit more detail of the cars like pricing

so focus £9999 how can add those details cos without damaging the program

[teknomage1]

You could make the values of the a-list lists, so that each key references a list

(defparameter *models* '(fiesta (ford $200 fast) focus (ford $300 slow)))
(getf *models* 'fiesta)
=> (FORD $200 FAST)
(cadr (getf *models* 'fiesta))
=> $200
(caddr (getf *models* 'fiesta))
=> FAST