Usage:
To build: clone. Navigate to the repo. make.
Developed under WSL for WSL. Might not work if not built and run on WSL. Might build under Cygwin (it does for me), which would allow running on windows.
Running the executable runs the interpreter in shell mode. Currently this is the only mode.
To run: "path/sixteenth" or if you are in the directory, "./sixteenth"
The command "./sixteenth < program.txt" causes the shell to loop. This is currently under investigation.
A forth word is any whitespace delimited stream of characters. Integers (e.g. -5 7 8) are pushed directly to the stack. Strings are not yet supported, but could probably be implemented (in forth) with some effort. The same goes for floats. But for the moment, everything on the stack is an integer.
To push to the stack: (i.e. press enter)
"." This word pops and prints the top of the stack, as an integer.
"EMIT" pops and prints as ASCII
"WORD" (experimental) prompts user input from stdin, converts to integer and pushes to the stack. Garbage in, garbage out (numerical only).
"VAR " Creates a variable "!" pops an address and a value (in that order) and stores the value to that address (ex VAR X 36 X ! stores 36 at the location of X)
"@" Pops an address and pushes the value at that address
"IF" begins a conditional IF block. MUST be terminated by a "THEN" ex "WORD 5 > IF something something THEN" "ELSE" must be used after an IF and inside a THEN-terminated conditional block.
"+" "-" ">" "<" ">=" "<=" "==" "!=" are arithmetic and logical operators. Each pops two arguments from the stack, and pushes their return value.
"WHILE" begins a WHILE loop. Takes a truth value.
"ENDWHILE" terminates a WHILE loop body, and also takes a truth value. That is, ENDWHILE checks whether the loop continues, so be sure to push your value before ENDWHILE.
":" indicates the beginning of a user-defined function, and ";" terminates its definition and also acts as a return (pops the address stack, which is not exposed to the user in general, at least if you are using the words as intended). e.g. : CR 10 EMIT ; defines carriage-return (prints newline).
"DUP" duplicates the top of the stack
"SWAP" swaps the top with top->next on the stack
"OVER" pushes a copy of the 2nd from the top of the stack to the stack
"DEPTH" returns the stack depth
"POP" pops the stack.
The following is an example program:
: CR 10 EMIT ; : SPACE 32 EMIT ; : FIRSTN DUP 0 OVER 0 > WHILE DUP . CR 1 + OVER OVER > ENDWHILE ;
: FIRSTNRECURSIVEREVERSE DUP . CR 1 - DUP 0 > IF FIRSTNRECURSIVEREVERSE THEN ;
35 FIRSTN 10 FIRSTNRECURSIVEREVERSE