Pi

Pi is a dialect of Brainfuck which encodes the commands of the program as erroneous digits of Pi number. The encoding works as follows: for each command a position is chosen in which it will be hidden. Then a table of commands and corresponding digits is constructed from the initial one

<   >   +   —   .   ,   [   ]
0   1   2   3   4   5   6   7   8

by shifting the row of commands one position to the right, starting with the command which is above the digit in this position. Thus, if the chosen position is second after decimal point, with digit 4 in it, the table will look like this:

<   >   +   —       .   ,   [   ]
0   1   2   3   4   5   6   7   8

After this the command is encoded with a digit below it, which replaces the correct digit in the chosen position. The resulting Pi program will be a number similar to Pi, but somewhat different from it.

To interpret Pi program, everything is done vice versa — for all positions in which Pi differs from the program, the Brainfuck commands are restored, and the result is interpreted as Brainfuck program.