Question

SCHEME :-)

1. [5 marks] Write a procedure called convert that takes as arguments: a temperature value (number), and two strings representing the input and output units respectively. The procedure should support conversions to or from any combination of Celcius ("C"), Fahrenheit ("F"), and Kelvin ("K"). Any other unit argument should result in the return of an error string.
   A table of temperature conversion equations and a calculator for verification can be found here.
   (Note: to compare strings in Scheme you can use the predicate (equal? str1 str2). To concatenate strings you can use the function (string-append str1 str2 ...).)
   E.g. (convert 32 "C" "F") → 89.6
   E.g. (convert 32 "apples" "oranges") → "Could not convert from apples to oranges"

Answer 1

(define (convert temp x y)
   (cond ((and (real? temp)
               (or (equal? "C" x) (equal? "F" x) (equal? "K" x))
               (or (equal? "C" y) (equal? "F" y) (equal? "K" y)))
           (cond
               ((and (equal? "C" x) (equal? "F" y)) (+ (* temp 1.8) 32))
               ((and (equal? "C" x) (equal? "K" y)) (+ temp 273.15))
               ((and (equal? "F" x) (equal? "C" y)) (/ (- temp 32) 1.8))
               ((and (equal? "F" x) (equal? "K" y)) (+ (/ (- temp 32) 1.8) 273.15))
               ((and (equal? "K" x) (equal? "C" y)) (- temp 273.15))
               ((and (equal? "K" x) (equal? "F" y)) (+ (* (- temp 273.15) 1.8) 32))
           ))
       (else "Could not convert from apples to oranges")
   )
)