Execute Brain****/Elena

<lang elena>#define system.

1. define extensions'text.

// --- Tape ---

1. class Tape

{

   #field theArray.
   #field thePointer.

   #constructor new &type'length:aLength
   [
       thePointer := Integer new:0.

       theArray := Array new &type'length:aLength &function: &&:n [ Integer new:0 ].
   ]

   #method type'tape = $self.

   #method append
   [
        (theArray@thePointer) += 1.
   ]
   
   #method reduce
   [
        (theArray@thePointer) -= 1.
   ]
   
   #method next
   [
       thePointer += 1.
   ]

   #method previous
   [
       thePointer -= 1.
   ]
   
   #method input
   [
       (theArray@thePointer) write &type'int:(console readChar).
   ]
   
   #method output
   [
       console write:(CharValue new:(theArray@thePointer)).
   ]
   
   #method get = theArray@thePointer.

}

// --- LoopInterpreter ---

1. class LoopInterpreter

{

   #field theLoopBody.
   #field theTape.
   
   #constructor new &tape:aTape
   [
       theTape := aTape.
       theLoopBody := String new.
   ]
   
   #method type'tape = theTape type'tape.

   #method append
   [
        theLoopBody += "+".
   ]
   
   #method reduce
   [
        theLoopBody += "-".
   ]
   
   #method next
   [
        theLoopBody += ">".
   ]

   #method previous
   [
        theLoopBody += "<".
   ]
   
   #method input
   [
        theLoopBody += ",".
   ]
   
   #method output
   [
        theLoopBody += ".".
   ]
   
   #method run
   [
       control while:[0 < theTape get ] &do:
           [ interpreter'Interpreter new:(theTape type'tape) eval:theLoopBody. ].
           
       ^ theTape.
   ]

}

// --- Interpreter ---

1. class Interpreter

{

   #field theTape.

   #constructor new : aTape
   [
       theTape := aTape.
   ]

   #method eval : anObject
   [
       $self eval::anObject.
   ]
       
   #method eval &type'widestr:aLiteral
   [
       control foreach:aLiteral &do:$self.
   ]

   #method eval &widechar:aChar
   [
       aChar =>
           ">" ? [ theTape next ]
           "<" ? [ theTape previous ]
           "+" ? [ theTape append ]
           "-" ? [ theTape reduce ]
           "." ? [ theTape output. ]
           "," ? [ theTape input. ]
           "[" ? [ theTape := LoopInterpreter new &tape:theTape. ]
           "]" ? [ theTape := theTape run. ].
   ]

}

// --- Program ---

1. symbol program =

[

   ('program'arguments Count == 1)?
       [  console write:"Please provide the path to the file to interpret". #throw BreakException new. ].
   
   textFileControl forEachLine:('program'arguments@1) &do:(Interpreter new:(Tape new &type'length:1024)).

]. </lang>