diff -r 4de31fdc0d67 -r b5b6ed38c2f2 solutions5/bfc.scala --- a/solutions5/bfc.scala Mon Nov 02 02:31:44 2020 +0000 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,317 +0,0 @@ -// Part 2 about a "Compiler" for the Brainf*** language -//====================================================== - -object CW10b { - -// !!! Copy any function you need from file bf.scala !!! -// -// If you need any auxiliary function, feel free to -// implement it, but do not make any changes to the -// templates below. - - -def time_needed[T](n: Int, code: => T) = { - val start = System.nanoTime() - for (i <- 0 until n) code - val end = System.nanoTime() - (end - start)/(n * 1.0e9) -} - -type Mem = Map[Int, Int] - - -import io.Source -import scala.util._ - -def load_bff(name: String) : String = - Try(Source.fromFile(name)("ISO-8859-1").mkString).getOrElse("") - -def sread(mem: Mem, mp: Int) : Int = - mem.getOrElse(mp, 0) - -def write(mem: Mem, mp: Int, v: Int) : Mem = - mem.updated(mp, v) - -def jumpRight(prog: String, pc: Int, level: Int) : Int = { - if (prog.length <= pc) pc - else (prog(pc), level) match { - case (']', 0) => pc + 1 - case (']', l) => jumpRight(prog, pc + 1, l - 1) - case ('[', l) => jumpRight(prog, pc + 1, l + 1) - case (_, l) => jumpRight(prog, pc + 1, l) - } -} - -def jumpLeft(prog: String, pc: Int, level: Int) : Int = { - if (pc < 0) pc - else (prog(pc), level) match { - case ('[', 0) => pc + 1 - case ('[', l) => jumpLeft(prog, pc - 1, l - 1) - case (']', l) => jumpLeft(prog, pc - 1, l + 1) - case (_, l) => jumpLeft(prog, pc - 1, l) - } -} - -def compute(prog: String, pc: Int, mp: Int, mem: Mem) : Mem = { - if (0 <= pc && pc < prog.length) { - val (new_pc, new_mp, new_mem) = prog(pc) match { - case '>' => (pc + 1, mp + 1, mem) - case '<' => (pc + 1, mp - 1, mem) - case '+' => (pc + 1, mp, write(mem, mp, sread(mem, mp) + 1)) - case '-' => (pc + 1, mp, write(mem, mp, sread(mem, mp) - 1)) - case '.' => { print(sread(mem, mp).toChar); (pc + 1, mp, mem) } - case '[' => - if (sread(mem, mp) == 0) (jumpRight(prog, pc + 1, 0), mp, mem) else (pc + 1, mp, mem) - case ']' => - if (sread(mem, mp) != 0) (jumpLeft(prog, pc - 1, 0), mp, mem) else (pc + 1, mp, mem) - case _ => (pc + 1, mp, mem) - } - compute(prog, new_pc, new_mp, new_mem) - } - else mem -} - -def run(prog: String, m: Mem = Map()) = compute(prog, 0, 0, m) - - -// The baseline to what we can compare our "compiler" -// implemented below. It should require something like -// 60 seconds for the calculation on my laptop -// -//time_needed(1, run(load_bff("benchmark.bf"))) - - - -// DEBUGGING INFORMATION!!! -// -// Compiler, even real ones, are fiedishly difficult to get -// to prduce correct code. The point is that for example for -// the sierpinski program, they need to still generate code -// that displays such a triangle. If yes, then one usually -// can take comfort that all is well. If not, then something -// went wrong during the optimisations. - - - -// (5) Write a function jtable that precomputes the "jump -// table" for a bf-program. This function takes a bf-program -// as an argument and Returns a Map[Int, Int]. The -// purpose of this map is to record the information -// that given on the position pc is a '[' or a ']', -// then to which pc-position do we need to jump next? -// -// For example for the program -// -// "+++++[->++++++++++<]>--<+++[->>++++++++++<<]>>++<<----------[+>.>.<+<]" -// -// we obtain the map -// -// Map(69 -> 61, 5 -> 20, 60 -> 70, 27 -> 44, 43 -> 28, 19 -> 6) -// -// This states that for the '[' on position 5, we need to -// jump to position 20, which is just after the corresponding ']'. -// Similarly, for the ']' on position 19, we need to jump to -// position 6, which is just after the '[' on position 5, and so -// on. The idea is to not calculate this information each time -// we hit a bracket, but just look up this information in the -// jtable. You can use the jumpLeft and jumpRight functions -// from Part 1 for calculating the jtable. -// -// Then adapt the compute and run functions from Part 1 in order -// to take advantage of the information stored in the jtable. -// This means whenever jumpLeft and jumpRight was called previously, -// you should look up the jump address in the jtable. - - -def jtable(pg: String) : Map[Int, Int] = - (0 until pg.length).collect { pc => pg(pc) match { - case '[' => (pc -> jumpRight(pg, pc + 1, 0)) - case ']' => (pc -> jumpLeft(pg, pc - 1, 0)) - }}.toMap - - -// testcase -// jtable("""+++++[->++++++++++<]>--<+++[->>++++++++++<<]>>++<<----------[+>.>.<+<]""") -// => Map(69 -> 61, 5 -> 20, 60 -> 70, 27 -> 44, 43 -> 28, 19 -> 6) - - -def compute2(pg: String, tb: Map[Int, Int], pc: Int, mp: Int, mem: Mem) : Mem = { - if (0 <= pc && pc < pg.length) { - val (new_pc, new_mp, new_mem) = pg(pc) match { - case '>' => (pc + 1, mp + 1, mem) - case '<' => (pc + 1, mp - 1, mem) - case '+' => (pc + 1, mp, write(mem, mp, sread(mem, mp) + 1)) - case '-' => (pc + 1, mp, write(mem, mp, sread(mem, mp) - 1)) - case '.' => { print(sread(mem, mp).toChar); (pc + 1, mp, mem) } - case '[' => - if (sread(mem, mp) == 0) (tb(pc), mp, mem) else (pc + 1, mp, mem) - case ']' => - if (sread(mem, mp) != 0) (tb(pc), mp, mem) else (pc + 1, mp, mem) - case _ => (pc + 1, mp, mem) - } - compute2(pg, tb, new_pc, new_mp, new_mem) - } - else mem -} - - -def run2(pg: String, m: Mem = Map()) = - compute2(pg, jtable(pg), 0, 0, m) - -//time_needed(1, run2(load_bff("benchmark.bf"))) - - - -// (6) Write a function optimise which deletes "dead code" (everything -// that is not a bf-command) and also replaces substrings of the form -// [-] by a new command 0. The idea is that the loop [-] just resets the -// memory at the current location to 0. In the compute3 and run3 functions -// below you implement this command by writing the number 0 to mem(mp), -// that is write(mem, mp, 0). -// -// The easiest way to modify a string in this way is to use the regular -// expression """[^<>+-.\[\]@*#]""", which recognises everything that is -// not a bf-command and replace it by the empty string. Similarly the -// regular expression """\[-\]""" finds all occurences of [-] and -// by using the Scala method .replaceAll you can repplace it with the -// string "0" standing for the new bf-command. - -def optimise(s: String) : String = { - s.replaceAll("""[^<>+-.\[\]@*#]""","") - .replaceAll("""\[-\]""", "0") -} - - -def compute3(pg: String, tb: Map[Int, Int], pc: Int, mp: Int, mem: Mem) : Mem = { - if (0 <= pc && pc < pg.length) { - val (new_pc, new_mp, new_mem) = pg(pc) match { - case '0' => (pc + 1, mp, write(mem, mp, 0)) - case '>' => (pc + 1, mp + 1, mem) - case '<' => (pc + 1, mp - 1, mem) - case '+' => (pc + 1, mp, write(mem, mp, sread(mem, mp) + 1)) - case '-' => (pc + 1, mp, write(mem, mp, sread(mem, mp) - 1)) - case '.' => { print(sread(mem, mp).toChar); (pc + 1, mp, mem) } - case '[' => - if (sread(mem, mp) == 0) (tb(pc), mp, mem) else (pc + 1, mp, mem) - case ']' => - if (sread(mem, mp) != 0) (tb(pc), mp, mem) else (pc + 1, mp, mem) - case _ => (pc + 1, mp, mem) - } - compute3(pg, tb, new_pc, new_mp, new_mem) - } - else mem -} - -def run3(pg: String, m: Mem = Map()) = { - val pg_opt = optimise(pg) - compute3(pg_opt, jtable(pg_opt), 0, 0, m) -} - - -// testcases - -//println(optimise(load_bff("collatz.bf"))) -//optimise(load_bff("benchmark.bf")) // should have inserted 0's -//optimise(load_bff("mandelbrot.bf")).length // => 11203 - -//time_needed(1, run3(load_bff("benchmark.bf"))) - - - -// (7) Write a function combine which replaces sequences -// of repated increment and decrement commands by appropriate -// two-character commands. For example for sequences of + -// -// orig bf-cmds | replacement -// ------------------------------ -// + | +A -// ++ | +B -// +++ | +C -// | -// ... | -// | -// +++....+++ | +Z -// (where length = 26) -// -// Similar for the bf-command -, > and <. All other commands should -// be unaffected by this change. -// -// Adapt the compute4 and run4 functions such that they can deal -// appropriately with such two-character commands. - -def splice(cs: List[Char], acc: List[(Char, Int)]) : List[(Char, Int)] = (cs, acc) match { - case (Nil, acc) => acc - case ('[' :: cs, acc) => splice(cs, ('[', 1) :: acc) - case (']' :: cs, acc) => splice(cs, (']', 1) :: acc) - case ('.' :: cs, acc) => splice(cs, ('.', 1) :: acc) - case ('0' :: cs, acc) => splice(cs, ('0', 1) :: acc) - case (c :: cs, Nil) => splice(cs, List((c, 1))) - case (c :: cs, (d, n) :: acc) => - if (c == d && n < 26) splice(cs, (c, n + 1) :: acc) - else splice(cs, (c, 1) :: (d, n) :: acc) -} - -def spl(s: String) = splice(s.toList, Nil).reverse - -//spl(load_bff("benchmark.bf")) - -def combine(s: String) : String = { - (for ((c, n) <- spl(s)) yield c match { - case '>' => List('>', (n + '@').toChar) - case '<' => List('<', (n + '@').toChar) - case '+' => List('+', (n + '@').toChar) - case '-' => List('-', (n + '@').toChar) - case _ => List(c) - }).flatten.mkString -} - - -//combine(load_bff("benchmark.bf")) - -def compute4(pg: String, tb: Map[Int, Int], pc: Int, mp: Int, mem: Mem) : Mem = { - if (0 <= pc && pc < pg.length) { - val (new_pc, new_mp, new_mem) = pg(pc) match { - case '0' => (pc + 1, mp, write(mem, mp, 0)) - case '>' => (pc + 2, mp + (pg(pc + 1) - '@'), mem) - case '<' => (pc + 2, mp - (pg(pc + 1) - '@'), mem) - case '+' => (pc + 2, mp, write(mem, mp, sread(mem, mp) + (pg(pc + 1) - '@'))) - case '-' => (pc + 2, mp, write(mem, mp, sread(mem, mp) - (pg(pc + 1) - '@'))) - case '.' => { print(sread(mem, mp).toChar); (pc + 1, mp, mem) } - case '[' => - if (sread(mem, mp) == 0) (tb(pc), mp, mem) else (pc + 1, mp, mem) - case ']' => - if (sread(mem, mp) != 0) (tb(pc), mp, mem) else (pc + 1, mp, mem) - case _ => (pc + 1, mp, mem) - } - compute4(pg, tb, new_pc, new_mp, new_mem) - } - else mem -} - -def run4(pg: String, m: Mem = Map()) = { - val pg_opt = combine(optimise(pg)) - compute4(pg_opt, jtable(pg_opt), 0, 0, m) -} - -// testcases -//println(combine(optimise(load_bff("collatz.bf")))) - -//combine(optimise(load_bff("benchmark.bf"))) // => """>A+B[A-A]