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[ brainfuck ]
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Introduction
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I recently learned the Standard ML programming language
and wrote a couple of rather small programs. One of them was an interpreter for the
esoteric programming language Brainfuck.
I've also written an interpreter in C which even does some slight optimizations. You can find the source code
of both programs below.
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Overview
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interpreter in SML
interpreter in C
links
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Interpreter in SML
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Here's the source code of the interpreter in SML. (GPL software.)
Some notes on the implementation:
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It's allowed to decrement the pointer below 0 and to increment it beyond 30000. However, dereferencing such a pointer
(i.e. using
+, -, ., ,, [, and ]) will result in a runtime error.
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+ and - just "wrap around" if the value of the dereferenced pointer (the pointer)
was less than 0 or greater than 255, respectively (i.e. "modulo 256").
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Syntax checking is done "on the fly". So
+[]], for example, won't find a syntax error because the (infinite) loop is executed
before it can find the unmatched bracket.
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# prints the values of the first ten cells of Brainfuck's array. This command is not part of the core language though it's provided
by several implementations for debugging purposes.
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Interpreter in C
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Here's the source code of the interpreter in C. (GPL software.)
Some notes on the implementation:
-
It's allowed to decrement the pointer below 0 and to increment it beyond 30000. However, dereferencing such a pointer
(i.e. using
+, -, ., ,, [, and ]) will result in a runtime error.
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The interpreter first parses the brainfuck code and internally replaces
multiple consecutive occurrences of the commands
>, <, +, and -, respectively, with one semantically equivalent command.
For example, instead of incrementing the pointer seven times only by one at a time, it gets incremented by seven at once.
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The positions of the matching brackets of
[ and ] will be stored in order to quickly jump to the corresponding bracket.
One can think of further optimizations. Feel free to adapt the code.
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Links
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