Page History

...

1. Try calling some the built-in operations like <=, =, and, or, not, equal? on various data values, e.g., is 17 times 18 bigger than 256?
2. What are the contracts of these built-in functions?
   *Choose any two, and write down the contract.
   *Verify your guess by asking the labby
   or by using DrScheme's Help Desk to look at the
   manual for the Beginning Student language.
   *Practice writing a function which returns a Boolean:
   Following the design recipe,
   write

   Code Block
   within-two?

   which takes in two numbers
   m and n, and returns true if
   m - n and {{ n - m}} are both
   less than 2.
   Otherwise, it should return false.
   (For learning purposes only, don't use Code Blockabs,
   which computes the absolute value. Also, don't use
   Code Blockcond or Code Blockif.)
   Your examples can look like

   Code Block
   (boolean=? (within-two? 99.8 101) true) (boolean=? (within-two? 5 -5) false)

...