What is the Befunge 93 ?
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.
For more informations, see the wikipedia page.
Instruction set
Flow direction:
- > Start moving right
- < Start moving left
- v Start moving down
- ^ Start moving up
- ? Start moving in a random direction
Matematical and logical operations:
- + Addition: pop a and b, and then push a+b
- - Subtraction: pop a and b, and then push b-a
- * Multiplication: pop a and b, and then push a*b
- / Division (integer): pop a and b, and then push b/a
- % Modulo: pop a and b, and then push b%a
[FIXME: if a=0, ask the user for the result]
- ! Logical NOT: pop a value. If the value is zero,
push 1; otherwise, push zero.
Tests:
- ` Greater than: pop a and b, then push 1 if b>a,
otherwise push zero.
Jumps:
- _ Pop a value; move right if value=0, left otherwise.
- | Pop a value; move down if value=0, up otherwise.
- # Skip the next cell
Stack operations:
- 0-9 Push the number on the stack
- : Duplicate value on top of the stack
- $ Pop a value from the stack
- \ Swap two values on top of the stack.
Input / Output:
- . Pop value and output as an integer.
- , Pop value and output as an ASCII character.
- p Put: pop y, x and v, then change the character at
the position (x,y) in the program to the character
with ASCII value v. [FIXME: Out of range]
- g Get: pop y and x, then push ASCII value of the
character at that position in the program
[FIXME: Out of range]
- & TODO (Not yet implemented).
- ~ TODO (Not yet implemented).
Other instructions:
- " Start string mode: push each character's ASCII
value all the way up to the next ".
- @ The end of the program.
Interesting links
