Pascal's Triangle

pascal.scm

(define (pascal row col)
  (define (row_underflow? col)    (< col 0))
  (define (row_overflow? row col) (> col row))
  (define (initial_cell? row)     (= row 0))
  
  (cond
    ((row_underflow? col)     0)
    ((row_overflow?  row col) 0)
    ((initial_cell?  row)     1)
    (else
      (+
        (pascal (- row 1) (- col 1))
        (pascal (- row 1) col)
      )
    )
  )
)