Syntactic Note

1
Syntactic Note

• Scheme excerpts in the The Schemers Guide have a
  slightly different syntax, for example
• (cond
• (null? A) ?empty)
• (null? B) (cons b ?())
• else ?full)

2
Syntactic Note

• (cond
• (null? A) ?empty)
• (null? B) (cons b ?())
• else ?full)
• becomes
• (cond
• ((null? A) 'empty)
• ((null? B) (cons b '()))
• (else 'full))

3
car/cdr vs. first/rest

• (define a (list 1 2 3 4))
• In Schemers Guide
• (first a) ? 1
• (rest a) ? '(2 3 4)
• In Scheme48
• (car a) ? 1
• (cdr a) ? '(2 3 4)

4
car/cdr vs. first/rest

• First/rest are synonymous with car/cdr
• (define first car)
• (define rest cdr)

5
List Processing

• Think of the list data structure as a sequence of
  values
• (define first-4-integers (list 1 2 3 4))
• We can write functions that operate on sequences
• sum, product, average
• Increment-each, square-each