numerals: 3 -4 5.3 3.5e3 3/4 3+4i
pre-defined procedures: + - * / min max
define "expression": (define x 3)
combinations: (+ 3 x)
making new procedures: (lambda (x) (+ x 3))
putting it together:
(define add-4 (lambda (y) (+ y 4))) (add-4 10) ((lambda (y) (+ y 4)) 10)