Class: SyntaxTree::Bf::Evaluate::Machine

Inherits:
Object
  • Object
show all
Defined in:
lib/syntax_tree/bf/evaluate.rb

Overview

This is the virtual machine that runs the set of instructions that the compiler outputs. Its state is kept on an infinite tape of memory, which is paired with a cursor.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(insns, stdin: STDIN, stdout: STDOUT) ⇒ Machine

Returns a new instance of Machine.



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# File 'lib/syntax_tree/bf/evaluate.rb', line 64

def initialize(insns, stdin: STDIN, stdout: STDOUT)
  @insns = insns
  @stdin = stdin
  @stdout = stdout
end

Instance Attribute Details

#insns ⇒ Object (readonly)

Returns the value of attribute insns.



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# File 'lib/syntax_tree/bf/evaluate.rb', line 62

def insns
  @insns
end

#stdin ⇒ Object (readonly)

Returns the value of attribute stdin.



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# File 'lib/syntax_tree/bf/evaluate.rb', line 62

def stdin
  @stdin
end

#stdout ⇒ Object (readonly)

Returns the value of attribute stdout.



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# File 'lib/syntax_tree/bf/evaluate.rb', line 62

def stdout
  @stdout
end

Instance Method Details

#run ⇒ Object 



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# File 'lib/syntax_tree/bf/evaluate.rb', line 70

def run
  pc = 0

  tape = Hash.new { 0 }
  cursor = 0

  while pc < insns.length
    insn = insns[pc]
    pc += 1

    case insn
    in [:inc]
      tape[cursor] += 1
    in [:dec]
      tape[cursor] -= 1
    in [:shr]
      cursor += 1
    in [:shl]
      cursor -= 1
    in [:inp]
      tape[cursor] = stdin.getc.ord
    in [:out]
      stdout.putc(tape[cursor].chr)
    in [:jmz, offset]
      pc = offset if tape[cursor] == 0
    in [:jmp, offset]
      pc = offset
    end
  end

  tape
end