bfgame is a brainfuck game engine (yes, seriously). This is its spec.
bfgame's memory space consists of a 'tape' with infinite cells, and a pointer, which you can move with the < and > operators.
In bfgame, each cell can hold an arbitrarily large integer.
The first five cells are reserved for the FFI.
bfgame has 8 instructions. The print(.) and input(,) operators have different functionalities than those in brainfuck:
. Run the currently selected function
, Get the next event from the event queue. If there are no events, this will be return 0.
+ Increment the current cell's value by 1
- Decrease the current cell's value by 1
> Move pointer to next cell
< Move pointer to previous cell (won't do anything if in cell #0)
[ Jump past the matching ] if the cell under the pointer is 0
] Jump back to the matching [ if the cell under the pointer is nonzero
Any other characters will be ignored by the interpreter, acting like comments.
To call external functions, you'll use the first 5 'tape' cells. Here's what each of them is used for:
0: Module ID - When you select a module, its functions become available
1: Function ID to call
2: Pointer to beginning of args - This should point to a cell which will be the first one in the functions arguments list. If there are no args, this should be 0.
3: Pointer to ending of args - If there are no args, this should be 0. If there is only one arg, it should be the same as #2.
4: Returned value - If a function returns a value, it'll go here.
Now, let's say we want to print the string "A" (ASCII codes 65). The function for this is function 1, and it's in the IO module (ID 1). It takes a list of any length and prints it, returning 0.
Example: Printing "A"
+ Load the IO module
> Move forward to cell #1
+ Add 1 to its value so it's now 1
> Move to cell #2
+++++ Add 5 to its value so it points to cell #5 which is where our string will start.
> Move to cell #3
+++++ Add 5 to its value which is where our string will end
>>> Move to cell #6 our loop counter
++++++ Set the loop counter to 6
[
<++++++++++ Go back to cell #5 and add 10
>- Go back to cell #6 and subtract 1
]
<+++++ Go back to cell #5 and add 5 so it's 65
<<<<. Go back to cell #1 and print it to run the function
Easy, right? :D