Re: [racket-users] recursive definition of a PROPOSITION

[Daniel Prager]

Hi Aysenur

Here are some hints:

   - It's simpler to work with symbols than strings in this sort of
   problem. E.g.

(define ops '(↔ → ∧ ⊕ ∨ ¬))
(define propositions '(P Q R X Y Z))


   - It helps to start by solving a simpler problem. Can you write a
   function (random-simple-expression) to randomly produce expressions with a
   single operation, using random propositions (no recursion required)? Sample
   output:

'(¬ P)
'(Q ⊕ R)

Solving this will set you on your way, give you a bit of confidence, and
hopefully prompt some ideas for solving the full problem.


   - Finally, seek the generalisation: (random-expression n). How will you
   use recursion to generate more complex structures, and keep count of the
   number of operations?


Dan

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[racket-users] recursive definition of a PROPOSITION

[Aysenur Türk]

(define( app L1 L2)
  (if(empty? L1) L2
 (cons (car L1) (app(cdr L1)L2

(app ((list "↔" "→" "∧" "⊕" "∨" "¬")) (list "P" "Q" "R" "S" "U" "X" "Y" "Z"))

(define L (list "↔" "→" "∧" "⊕" "∨" "¬"))
(define ( f L n)
  (if (= n 0) "p"
  (string-append "p" (car L) (f(cdr L) (- n 1)

(f L 3)

You have the following recursive definition of a PROPOSITION:

T, F are propositions ( truth value of propositional variables) List item 
Propositional letters P, Q , R, S,U,X, Y, Z   are propositions. If A is a 
proposition the ¬A is a proposition. If A and B are propositions then A⊕B , A→B 
, A∧B, A∨B , A↔B are propositions. Write a DrRacket procedure that will 
randomly generate a proposition with a given number of operations .

2 formulas calculated by your program (the formulas must contain 3 different 
variables and 6 operatıons .

Hi everyon I'm new here.Can anyone help me for this problem ? I tried the solve 
it but it's probably wrong I didn't understand clearly because I'm a new in 
racket programming language.Thanks in advance for your answers !!

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