Comparing strings (scheme)

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June 13th, 2006, 04:54 PM

xlordt

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Comparing strings (scheme)

For some reason i keep getting Access Denied in this little snippet

Code:

(display "Please enter your Username: ") ;Display Username Message
 (define n (read)) (newline) ;Read input from buffer
 
(display "Please enter your Password: ") ;Display Password Message
 (define p (read)) (newline) ;Read input from buffer

 (if (eq? p "a123456") ;Check to make sure that the password is correct
  (display "Access Granted") ;Grant access
  (display "Access Denied"))

Anyone knows why?

June 13th, 2006, 05:28 PM

Yegg`

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Here is my solution:

Code:

(define password 'a123456)

(define (ask-username)
        (display "Account: ")
	(read))

(define (ask-password)
	(display "Password: ")
	(if (equal? password (read))
	    "Granted!"
	    "Denied!"))

(define (get-info)
        (let ((pas (ask-password))
	      (acc (ask-username)))
	     '(acc pas)))

(ask-username) stores whatever the user enters in after Account: into the variable acc.
(ask-password) stores whatever the user enters in after Password: into the variable pas.
(get-info) creates the two variables (acc and pas) and returns a list containing both items.

This is just one solution.

Last edited by Yegg` : June 13th, 2006 at 05:38 PM.

June 13th, 2006, 05:33 PM

netytan

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This works. The problem is that (read) returns lisp code not a string so you need to compare symbols

Code:

(display "Please enter your Username: ") ;Display Username Message
(define n (read))

(newline)
 
(display "Please enter your Password: ") ;Display Password Message
(define p (read))

(newline)

(display (if (eq? p 'a123456)
             "Access Granted"
             "Access Denied"))

If you want to get input as a string then you have to write your own little function to read until a newline is given

. The advantage of this is that you have more control over the language: if you don't want the newline character on the end then you wont get it and hence don't have to strip it.

Hope this helps man,

Mark.

Comments on this post

LinuxPenguin agrees: Great answer, mark

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