Rec

This repository holds the Python & C interpreters for Rec. (Though I don't want to maintain the Python interpreter anymore.)

rec.c is a C interpreter of Rec with a REPL and debugger. (You can compile it with a compiler that supports C99.)

rec.py is my (abandoned) Rec interpreter in Python.

Command Summary

The language is summarized below:

Command	Behavior
123	Push the non-negative number onto the stack.
/	Successor; increment TOS.
\	Predecessor; decrement TOS.
:	Load; Pops x, pushes stack[~x].
;	Store; Pops v and x. Assigns stack[~x] to v.
[ ... ]	Infinite loop; executes ... forever.
^	Pops x. If x == 0, break out of the innermost [ ... ] loop. (Or terminates program, if not in a [ ... ] loop.)

Interpreter Spec

Both interpreters here have a REPL (which you can access with no CLI arguments) and a debugger (which you may enter by adding breakpoints b in the program).

Use Enter to step through the debugger.

You can use Ctrl-D to exit the REPL or the debugger.

Added Commands

• P: Pop & print TOS as integer.
• R: Read an integer from input, and push the value.
• p: Pop & print TOS as a char.
• r: Read a char from input, and push the ord value.
• s: Prints the entire stack at the current point of execution.
• b: Breakpoint; starts debugger at this part of program.

Commands in the debugger (C interpreter)

• \n: Step to next iteration.
• c: Continue execution until the next breakpoint.
• m: If current char is [, hide debugging information until the matching ].
• q: Quit; Exit the debugger. (You can also use Ctrl-D to exit.)

Pitfalls

• -1 is represented by 0\, not 1\ (which is 0)!
• ; pops 2 values from the stack!
  • E.g. [1 2 3 0 1]: when ; is called, the new TOS is 3, not 0. So this will turn the stack to [1 0 3].
• : and ; look similar (and are easily confusable), so be careful.

See also

• Recur interpreter (written by laerling), where you can find some examples of an old version of this language.
• Rec+