[−][src]Module sbrain::specification
What is SBrain?
SBrain, or Semantic Brain, is a language based on Urban Müller's famous language with only 8 symbols (3 bit instructions). SBrain's additions increase the number of symbols to 16 (4 bit instructions) and adds a stack and a register.
Specification
Data Structures
SBrain requires:
- a read/write data tape which is addressable up to, at minimum, 65,536 (0x0 - 0xFFFF) 32-bit cells. They must be initially set to zero.
- a read/write data stack with room for at least 256 values. They must be initially set to zero.
- a read-only tape which contains the executable code. This code is represented as a list of unsigned integers of, at minimum, six bits in width.
- a read-only nonreversable tape containing the program's input (a function like
getch()works fine.) - a write-only nonreversable tape containing the program's output (a function like
putch()works fine.) - a read/write register (
data_p) of enough bits to store a position on the data tape - a read/write register (
inst_p) of enough bits to store a position on the instruction tape - a read/write register (
auxi_r) of the same size as a cell on the data tape
Commands and Source Code
SBrain source code consists of text characters. Executable code consists of unsigned integers of four bits. A transliterator converts the source code to executable code by a one-to-one mapping, with one exception: all data between # characters, including those characters, is ignored by the transliterator.
The first eight instructions are the standard brainf--- instructions. Any brainf--- program is a valid SBrain program and should behave in the same way as in a standard, semantically equivalent brainf--- interpreter, so long as comments are properly escaped.
| Decimal | Code | Semantics |
|---|---|---|
| 0 | < | Decrement data_p |
| 1 | > | Increment data_p |
| 2 | - | Subtract one from the cell pointed at by data_p |
| 3 | + | Add one to the cell pointed at by data_p |
| 4 | [ | If the cell pointed at by data_p is zero, move inst_p to point to the matching ], plus one, or NOP if there is none. |
| 5 | ] | If the cell pointed at by data_p is nonzero, move inst_p to point to the matching ], plus one, or NOP if there is none. |
| 6 | . | Place the value in the cell pointed at by data_p on the output tape |
| 7 | , | Place the next value from the input tape in the cell pointed at by data_p |
| 8 | { | Push the value from the cell pointed at by data_p onto the stack |
| 9 | } | Pop the next value from the stack into the cell pointed at by data_p |
| 10 | ( | Set auxi_r to the value of the cell pointed at by data_p |
| 11 | ) | Set the cell pointed at by data_p to the value in auxi_r |
| 12 | ^ | Set the value in auxi_r to 0 |
| 13 | ! | Perform a bitwise NOT on the value in auxi_r. |
| 14 | & | Perform a bitwise AND on the value in auxi_r and the cell pointed at data_p, placing the value in auxi_r. |
| 15 | @ | End the program. The exit code is the value in auxi_r. |
Further Rules
No read operation shall ever disrupt a cell on the data tape.
Reading an EOF always produces a 0.
Non-command characters in the instruction section of source code must be ignored.
In the case of the instruction pointer running off the end of the tape, it must wrap to the beginning.