Question

How to implement "let" expression in a new environment and evaluate the body of the let in the new environment using Racket language scheme. "let" must evaluate the expressions that determine the values of the variables bound by the let and the body of a let is a sequence of expressions.

Example Test Case:

(equal? (special-let '(let ((x 1) (y 2)) (+ x y))) 3)

Answer 1

Syntax : let( [id val-expr]....body)

It evaluates the val-exprs left-to-right, creates a new location for each id, and places the values into the locations. It then evaluates the bodys, in which the ids are bound. The last body expression is in tail position with respect to the let form.

Example:

1. (let([x 5]) x)

ans:   5

2.

(let ([x 5])

(let([x 2])

[y x])

(list y x)))

ans: (5 2)