// Core Part about an Interpreter for +
−
// the Brainf***++ language+
−
//==============================================+
−
+
−
+
−
object CW10a {+
−
+
−
+
−
// representation of Bf memory +
−
+
−
type Mem = Map[Int, Int]+
−
+
−
+
−
// (1) Write a function that takes a file name as argument and+
−
// and requests the corresponding file from disk. It Returns the+
−
// content of the file as a String. If the file does not exists,+
−
// the function should Return the empty string.+
−
+
−
import io.Source+
−
import scala.util._+
−
import java.io.FileNotFoundException+
−
import scala.annotation.tailrec+
−
+
−
def load_bff(name: String) : String = {+
−
    try {+
−
        val bff = io.Source.fromFile(name).getLines().mkString(" ")+
−
        bff+
−
    }+
−
    catch {+
−
        case ex: FileNotFoundException =>+
−
        val bff = ""+
−
        bff+
−
    }+
−
}+
−
+
−
+
−
+
−
// (2) Complete the functions for safely reading  +
−
// and writing brainf***++ memory. Safely read should+
−
// Return the value stored in the Map for a given memory+
−
// pointer, provided it exists; otherwise it Returns 0. The+
−
// writing function generates a new Map with the+
−
// same data, except at the given memory pointer the+
−
// value v is stored.+
−
+
−
+
−
def sread(mem: Mem, mp: Int) : Int = {+
−
    mem.getOrElse(mp,0)+
−
}+
−
+
−
def write(mem: Mem, mp: Int, v: Int) : Mem = {+
−
    val newMem = mem + (mp -> v)+
−
    newMem+
−
}+
−
+
−
+
−
+
−
// (3) Implement the two jumping instructions in the +
−
// brainf***++ language. In jumpRight, given a program and +
−
// a program counter move the program counter to the right +
−
// until after the *matching* ]-command. Similarly, +
−
// jumpLeft implements the move to the left to just after+
−
// the *matching* [-command.+
−
@tailrec+
−
def jumpRight(prog: String, pc: Int, level: Int) : Int = {+
−
    if (pc > prog.length-1) pc+
−
    else {+
−
        prog(pc) match{+
−
            case '[' => jumpRight(prog, pc+1, level+1)+
−
            case ']' => if (level == 0) pc+1+
−
                        else jumpRight(prog, pc+1, level-1)+
−
            case _ => jumpRight(prog, pc+1, level)+
−
        }+
−
    }+
−
}+
−
@tailrec+
−
def jumpLeft(prog: String, pc: Int, level: Int) : Int = {+
−
    if (pc < 0) pc +
−
    else {+
−
        prog(pc) match{+
−
            case ']' => jumpLeft(prog, pc-1, level+1)+
−
            case '[' => if (level == 0) pc+1+
−
                        else jumpLeft(prog, pc-1, level-1)+
−
            case _ => jumpLeft(prog, pc-1, level)+
−
        }+
−
    }+
−
}+
−
+
−
+
−
// testcases+
−
//jumpRight("""--[..+>--],>,++""", 3, 0)         // => 10+
−
//jumpLeft("""--[..+>--],>,++""", 8, 0)          // => 3+
−
// jumpRight("""--[..[+>]--],>,++""", 3, 0)       // => 12+
−
// jumpRight("""--[..[[-]+>[.]]--],>,++""", 3, 0) // => 18+
−
//jumpRight("""--[..[[-]+>[.]]--,>,++""", 3, 0)  // => 22 (outside)+
−
//jumpLeft("""[******]***""", 7, 0)              // => -1 (outside)+
−
+
−
+
−
+
−
// (4) Complete the compute function that interprets (runs) a brainf***+++
−
// program: the arguments are a program (represented as a string), a program +
−
// counter, a memory counter and a brainf***++ memory. It Returns the+
−
// memory at the stage when the execution of the brainf***++ program+
−
// finishes. The interpretation finishes once the program counter+
−
// pc is pointing to something outside the program string.+
−
// If the pc points to a character inside the program, the pc, +
−
// memory pointer and memory need to be updated according to +
−
// rules of the brainf***++ language. Then, recursively, the compute +
−
// function continues with the command at the new program+
−
// counter. +
−
//+
−
// Implement the run function that calls compute with the program+
−
// counter and memory counter set to 0.+
−
+
−
@tailrec+
−
def compute(prog: String, pc: Int, mp: Int, mem: Mem) : Mem = {+
−
    if (pc > prog.length-1) mem+
−
    else {+
−
        prog(pc) match{+
−
            case '>' => compute(prog, pc+1, mp+1, mem)+
−
            case '<' => compute(prog, pc+1, mp-1, mem)+
−
            case '+' => compute(prog, pc+1, mp,write(mem,mp,sread(mem,mp)+1))+
−
            case '-' => compute(prog, pc+1, mp,write(mem,mp,sread(mem,mp)-1))+
−
            case '.' => print(sread(mem,mp).toChar)+
−
                        compute(prog, pc+1, mp, mem)+
−
            case '[' => if (sread(mem,mp) == 0) compute(prog,jumpRight(prog,pc+1,0),mp,mem)+
−
                        else compute(prog,pc+1,mp,mem)+
−
            case ']' => if (sread(mem,mp) != 0) compute(prog,jumpLeft(prog,pc-1,0),mp,mem)+
−
                        else compute(prog,pc+1,mp,mem)+
−
            case '*' => compute(prog, pc+1,mp, write(mem,mp,sread(mem,mp)*sread(mem,mp-1)))+
−
            case '@' => compute(prog,pc+1,mp, write(mem,sread(mem,mp),sread(mem,mp-1)))+
−
            case '#' => print(sread(mem,mp))+
−
                        compute(prog,pc+1, mp, mem)+
−
            case _ => compute(prog,pc+1,mp,mem)+
−
        }+
−
    }+
−
}+
−
+
−
def run(prog: String, m: Mem = Map()) : Mem = {+
−
    compute(prog, 0, 0, m)+
−
}+
−
+
−
+
−
+
−
// some sample bf/bf++-programs collected from the Internet+
−
//==========================================================+
−
+
−
+
−
// some contrived (small) programs+
−
//---------------------------------+
−
+
−
// clears the 0-cell+
−
//run("[-]", Map(0 -> 100))    // Map will be 0 -> 0+
−
+
−
// moves content of the 0-cell to 1-cell+
−
//run("[->+<]", Map(0 -> 10))  // Map will be 0 -> 0, 1 -> 10+
−
+
−
+
−
// copies content of the 0-cell to 2-cell and 4-cell+
−
//run("[>>+>>+<<<<-]", Map(0 -> 42))    // Map(0 -> 0, 2 -> 42, 4 -> 42)+
−
+
−
+
−
// prints out numbers 0 to 9+
−
//run("""+++++[->++++++++++<]>--<+++[->>++++++++++<<]>>++<<----------[+>.>.<+<]""")+
−
+
−
// bf++ program calculating the cube-function, 10 * 10 * 10 = 1000+
−
//run("""++++++++++#>+***#""")           // Map(0 -> 10, 1 -> 1000)+
−
+
−
+
−
// bf++ program copies 3 from 0-cell to to cells 1, 4, 5, 6 and 7+
−
// (note that because of how the program wprks cell 1 will contain 7) +
−
//run("""+++>+@+@+@+@+@""")   // Map(0 -> 3, 1 -> 7, 4 -> 3, 5 -> 3, 6 -> 3, 7 -> 3)+
−
+
−
+
−
+
−
// some more "useful" programs+
−
//-----------------------------+
−
+
−
// hello world program 1+
−
// run("""++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.++++++++
−
//       ..+++.>>.<-.<.+++.------.--------.>>+.>++.""")+
−
+
−
// hello world program 2+
−
// run("""++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++
−
//       +.<<+++++++++++++++.>.+++.------.--------.>+.>.""")+
−
+
−
// hello world program 3+
−
// run("""+++++++++[>++++++++>+++++++++++>+++++<<<-]>.>++.+++++++..+
−
//       +++.>-.------------.<++++++++.--------.+++.------.--------.>+.""")+
−
+
−
 +
−
// draws the Sierpinski triangle+
−
//run(load_bff("sierpinski.bf"))+
−
+
−
+
−
//fibonacci numbers below 100+
−
// run("""++++++++++++
−
//      >+>>>>+++++++++++++++++++++++++++++++++++++++++++++
−
//      >++++++++++++++++++++++++++++++++<<<<<<[>[>>>>>>+>+
−
//      +<<<<<<<-]>>>>>>>[<<<<<<<+>>>>>>>-]<[>++++++++++[-+
−
//      <-[>>+>+<<<-]>>>[<<<+>>>-]+<[>[-]<[-]]>[<<[>>>+<<<+
−
//      -]>>[-]]<<]>>>[>>+>+<<<-]>>>[<<<+>>>-]+<[>[-]<[-]]+
−
//      >[<<+>>[-]]<<<<<<<]>>>>>[++++++++++++++++++++++++++
−
//      +++++++++++++++++++++++.[-]]++++++++++<[->-<]>+++++
−
//      ++++++++++++++++++++++++++++++++++++++++++++.[-]<<+
−
//      <<<<<<<<<<[>>>+>+<<<<-]>>>>[<<<<+>>>>-]<-[>>.>.<<<+
−
//      [-]]<<[>>+>+<<<-]>>>[<<<+>>>-]<<[<+>-]>[<+>-]<<<-]""")+
−
+
−
//outputs the square numbers up to 10000+
−
// run("""++++[>+++++<-]>[<+++++>-]+<+[>[>+>+<<-]++>>[<<+>>-]>>>[-]++>[-]++
−
//       >>>+[[-]++++++>>>]<<<[[<++++++++<++>>-]+<.<[>----<-]<]+
−
//       <<[>>>>>[>>>[-]+++++++++<[>-<-]+++++++++>[-[<->-]+[<<<]]<[>+<-]>]<<-]<<-]""")+
−
+
−
+
−
// calculates 2 to the power of 6+
−
//(example from a C-to-BF compiler at https://github.com/elikaski/BF-it)+
−
// run(""">>[-]>[-]++>[-]++++++><<<>>>>[-]+><>[-]<<[-]>[>+<<+>-]>[<+>-]+
−
//       <><[-]>[-]<<<[>>+>+<<<-]>>>[<<<+>>>-][-]><<>>[-]>[-]<<<[>>[-]+
−
//       <[>+>+<<-]>[<+>-]+>[[-]<-<->>]<<<-]>>[<<+>>-]<<[[-]>[-]<<[>+>+
−
//       +<<-]>>[<<+>>-][-]>[-]<<<<<[>>>>+>+<<<<<-]>>>>>[<<<<<+>>>>>-]+
−
//       <<>>[-]>[-]<<<[>>>+<<<-]>>>[<<[<+>>+<-]>[<+>-]>-]<<<>[-]<<[-]+
−
//       >[>+<<+>-]>[<+>-]<><[-]>[-]<<<[>>+>+<<<-]>>>-[<<<+>>>-]<[-]>[-]+
−
//       <<<[>>+>+<<<-]>>>[<<<+>>>-][-]><<>>[-]>[-]<<<[>>[-]<[>+>+<<-]>+
−
//       [<+>-]+>[[-]<-<->>]<<<-]>>[<<+>>-]<<][-]>[-]<<[>+>+<<-]>>[<<+>+
−
//       >-]<<<<<[-]>>>>[<<<<+>>>>-]<<<<><>[-]<<[-]>[>+<<+>-]>[<+>-]<>+
−
//       <[-]>[-]>[-]<<<[>>+>+<<<-]>>>[<<<+>>>-]<<>>[-]>[-]>[-]>[-]>[-]>+
−
//       [-]>[-]>[-]>[-]>[-]<<<<<<<<<<>>++++++++++<<[->+>-[>+>>]>[+[-<++
−
//       >]>+>>]<<<<<<]>>[-]>>>++++++++++<[->-[>+>>]>[+[-<+>]>+>>]<<<<<+
−
//       ]>[-]>>[>++++++[-<++++++++>]<.<<+>+>[-]]<[<[->-<]++++++[->+++++
−
//       ++++<]>.[-]]<<++++++[-<++++++++>]<.[-]<<[-<+>]<<><<<""")+
−
+
−
+
−
+
−
// a Mandelbrot set generator in brainf*** written by Erik Bosman+
−
// (http://esoteric.sange.fi/brainfuck/utils/mandelbrot/)+
−
//+
−
//run(load_bff("mandelbrot.bf"))+
−
+
−
+
−
// a benchmark program (counts down from 'Z' to 'A')+
−
//+
−
//run(load_bff("benchmark.bf"))+
−
+
−
// calculates the Collatz series for numbers from 1 to 30+
−
//+
−
//run(load_bff("collatz.bf"))+
−
+
−
}+
−