Befunge
Befunge is a stack-based, reflective, esoteric programming language. It differs from conventional languages in that programs are arranged on a two-dimensional grid. "Arrow" instructions direct the control flow to the left, right, up or down, and loops are constructed by sending the control flow in a cycle.
This implementation is based upon the following references:
Usage
$ ruby befunge.rb <filename>
Included
- 3 Hello World examples:
helloworld, 2 and 3.bf - A quine:
quine.bf - A direction checker:
flowcheck.bf - A less or more game that allows you to cheat
less_or_more.bf - A factorial program:
factorial.bf
Instruction Set
| Cmd | Description |
|---|---|
+
|
Addition: Pop two values a and b, then push the result of a+b |
-
|
Subtraction: Pop two values a and b, then push the result of b-a |
*
|
Multiplication: Pop two values a and b, then push the result of a*b |
/
|
Integer division: Pop two values a and b, then push the result of b/a, rounded down. According to the specifications, if a is zero, ask the user what result they want. |
%
|
Modulo: Pop two values a and b, then push the remainder of the integer division of b/a. |
!
|
Logical NOT: Pop a value. If the value is zero, push 1; otherwise, push zero. |
`
|
Greater than: Pop two values a and b, then push 1 if b>a, otherwise zero. |
>
|
PC direction right |
<
|
PC direction left |
^
|
PC direction up |
v
|
PC direction down |
?
|
Random PC direction |
_
|
Horizontal IF: pop a value; set direction to right if value=0, set to left otherwise |
|
|
Vertical IF: pop a value; set direction to down if value=0, set to up otherwise |
"
|
Toggle stringmode (push each character's ASCII value all the way up to the next ")
|
:
|
Duplicate top stack value |
\
|
Swap top stack values |
$
|
Pop (remove) top stack value and discard |
.
|
Pop top of stack and output as integer |
,
|
Pop top of stack and output as ASCII character |
#
|
Bridge: jump over next command in the current direction of the current PC |
g
|
A "get" call (a way to retrieve data in storage). Pop two values y and x, then push the ASCII value of the character at that position in the program. If (x,y) is out of bounds, push 0 |
p
|
A "put" call (a way to store a value for later use). Pop three values y, x and v, then change the character at the position (x,y) in the program to the character with ASCII value v |
&
|
Get integer from user and push it |
~
|
Get character from user and push it |
@
|
End program |
0 – 9
|
Push corresponding number onto the stack |