mirror of
https://github.com/zekexiao/pocketlang.git
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114 lines
3.9 KiB
Plaintext
114 lines
3.9 KiB
Plaintext
from lang import write
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###############################################################################
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## BRAINFUCK IMPLEMENTATION IN POCKETLANG ##
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###############################################################################
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## Reference: https://en.wikipedia.org/wiki/Brainfuck
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## Note that this interpreter implementation is just to test pocketlang and is
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## not an efficient one. This could be optimized by evaluvating the expressions
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## at "compile time" (AOT) to avoid re-evaluvating those expressions at runtime
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## and also we can pre compile the loop jump offsets.
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## Source: https://en.wikipedia.org/wiki/Brainfuck
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hello_world = "++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]
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>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++."
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## Source: https://github.com/fabianishere/brainfuck/blob/master/examples/asciiart/triangle.bf
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## Madeby: Nyyrikki(2002)
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triangle = ">++++[<++++++++>-]>++++++++[>++++<-]>>++>>>+>>>+<<<<<<<<<<[-[->+<]>
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[-<+>>>.<<]>>>[[->++++++++[>++++<-]>.<<[->+<]+>[->++++++++++<<+>]>.
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[-]>]]+<<<[-[->+<]+>[-<+>>>-[->+<]++>[-<->]<<<]<<<<]++++++++++.+++.
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[-]<]+++++"
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## Source: https://github.com/fabianishere/brainfuck/blob/master/examples/math/fib.bf
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fibonacci = ">++++++++++>+>+[[+++++[>++++++++<-]>.<++++++[>--------<-]+<<<]>.
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>>[[-]<[>+<-]>>[<<+>+>-]<[>+<-[>+<-[>+<-[>+<-[>+<-[>+<-[>+<-[>+
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<-[>+<-[>[-]>+>+<<<-[>+<-]]]]]]]]]]]+>>>]<<<]"
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execute(hello_world)
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execute(triangle)
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##execute(fibonacci) This will run endlessly (cannot run test).
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###############################################################################
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## INTERNAL ##
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###############################################################################
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def execute(expr)
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ptr = 0 ## Data pointer.
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mem = [0] ## Data / Memory
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i = 0 ## Instruction pointer
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while true
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c = expr[i] ## Current char.
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## Increment the data pointer (to point to the next cell to the right).
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if c == '>'
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ptr += 1
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if ptr >= mem.length then list_append(mem, 0) end
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## Decrement the data pointer (to point to the next cell to the left).
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elif c == '<'
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ptr -= 1
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if ptr < 0 then assert(false, "ip < 0") end
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## Increment (increase by one) the byte at the data pointer.
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elif c == '+'
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if mem[ptr] == 255 then mem[ptr] = 0
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else mem[ptr] += 1 end
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## Decrement (decrease by one) the byte at the data pointer.
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elif c == '-'
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if mem[ptr] == 0 then mem[ptr] = 255
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else mem[ptr] -= 1 end
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## output the byte at the data pointer.
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elif c == '.'
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write(str_chr(mem[ptr]))
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elif c == ','
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assert(false, "Currently input isn't supported in pocketlang.")
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## if the byte at the data pointer is zero, then instead of moving the
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## instruction pointer forward to the next command, jump it forward to
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## the command after the matching ] command.
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elif c == '[' and mem[ptr] == 0
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open = 0
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while true
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i += 1
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if expr[i] == ']' and open == 0 then break end
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if expr[i] == '[' then open += 1
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elif expr[i] == ']' then open -= 1
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end assert(open >= 0)
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end
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## if the byte at the data pointer is nonzero, then instead of moving the
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## instruction pointer forward to the next command, jump it back to the
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## command after the matching [ command
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elif c == ']' and mem[ptr] != 0
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open = 0
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while true
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i -= 1
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if expr[i] == '[' and open == 0 then break end
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if expr[i] == ']' then open -= 1
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elif expr[i] == '[' then open += 1
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end assert(open <= 0)
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end
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else
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## Any other characters are ignored in brainfuck interpreter.
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end
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## Increment the instruction pointer by one.
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## If we reached the end terminate.
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i += 1
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if i == expr.length then break end
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end
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end
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