11-30-2014
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2.18 is reverse ,that I got abstract thinking, using append take place cons,form this exercise.
2.27 is deep-reverse ,than I know deal different abstract data needs different process like pair? to comb-list, null? to list.

But ,i don't relly know about pair? . can you give me a little advise?
Merge pull request #2 from xhjinuuu/master

NA