SICP Exercise 3.6 reset random number generator

Exercise 3.6.  It is useful to be able to reset a random-number generator to produce a sequence starting from a given value. Design a new rand procedure that is called with an argument that is either the symbol generateor the symbol reset and behaves as follows: (rand 'generate) produces a new random number; ((rand 'reset) <new-value>) resets the internal state variable to the designated <new-value>. Thus, by resetting the state, one can generate repeatable sequences. These are very handy to have when testing and debugging programs that use random numbers.

 SOLUTION

The code is here:

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