Equal? as a procedure

Two lists are said to be equal? if they contain equal elements arranged in the same order. For example,

(equal? '(this is a list) '(this is a list))

is true, but

(equal? '(this is a list) '(this (is a) list))

is false. To be more precise, we can define equal? recursively in terms of the basic eq? equality of symbols by saying that a and b are equal if they are both symbols and the symbols are eq? , or if they are both lists such that (car a) is equal? (car b) and (cdr a) is equal? (cdr b) . Using this idea, implement equal? as a procedure equal-proc? .

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