Expression

666,(+ 4 5) is typical scheme expression.(+ 4 5 6) is same as (+ (+ 4 5) 6).

Evaluation order

Normal order(greedy)

The interpreter first evaluates the operator and operands and the applies the resulting procedure to the resulting arguments.

Applicative order(lazy)

Not evaluate the operands until their value were needed.Instead it would extend the expression to only primitive operator.The evaluate the expression.

Naming Expression

(define (<symbol> <formal parameters>) <expression>) (define size 2) naming 2 by size.

Environment

The predefined name-object paris.

Condition Expression

1. cond for conditional expression. scheme (cond (<p0> <e0>) (<p1> <e1>) ... (<pn> <en>) (else <e>) )
2. if for conditional expression. scheme (if <predicate> <consequent> <alternative>)
3. logic operator for conditional expression. scheme (and <e0> <e1> ... <en>) (or <e0> <e1> ... <en>) (not <e>)