Support for the P" programming language

[dreasgrech]

http://en.wikipedia.org/wiki/P%E2%80%B2%E2%80%B2

An excerpt from Wikipedia:

Böhm1 gives the following program to compute the predecessor (x-1) of an integer x > 0:

R ( R ) L ( r' ( L ( L ) ) r' L ) R r

which translates directly to the equivalent brainfuck program

> [ > ] < [ −  [ < [ < ] ] −  < ] > +

The program expects an integer to be represented in bijective base-n notation, with a1, ..., an coding the digits 1,...,n, respectively, and to have an a0 before and after the digit-string. (E.g. in bijective base-2, the number eight would be encoded as a0a1a1a2a0, because 8 = 1_22 + 1_21 + 2*20.) At the beginning and end of the computation, the tape-head is on the a0 preceding the digit-string.