short for the magic book
here is the place I keep and display my practices for SICP
todo!!
for testing the code, in the forth chapter, ex4.table.rkt and ex4.03.rkt is from
https://wizardbook.wordpress.com/2010/12/25/exercise-4-3/
Most of the practice done here is tested with drracket, with the #lang planet neil/sicp,some with plainly #lang racket or #lang sicp