!759

static boolean printNulls = true, full = false;

static L<S> inputs = toLinesFullTrim([[

  hello

  "hello!"

  hello you

  hello < you

  [hello]

  [hello] [you]

  [hello < you]

  [ ? < Is < it < safe < to < allow [PowerTOP] to [make < all < the < changes < located on < the < Tunables < tab] ]

  [ I < was < going to < create < a < startup script < for < it ]

]]);

static S snlRules = [[

  // highest (strongest binding) level 

  <identifier> = idword

  <quoted> = subword

  ? = idword

  ! = idword

  <subword> = word

  <idword> = word

  // juxtaposition on highest level

  <word> <word> = word

  // bracketing takes us to highest level

  [ <lowest> ] = subword

  ( <lowest> ) = subword

  // < is intermediate

  <word> = arrows

  <word> < <arrows> = arrows

  = lowest // allow empty here

  <arrows> = lowest

]];

static class SNL {

  S op;

  new L<SNL> subs;

  *() {}

  *(S op) {}

  *(S op, L<SNL> *subs) {}

}

p {

  for (S input : inputs) {

    SNL snl = parseSNL(input);

    print();

    print("PARSING: " + input);

    print();

    print("  " + structure(snl));

    print();

  }

}

static SNL parseSNL(S input) {

  Explain exp = explainFull(input, snlRules, "lowest");

  ret explainToSNL(exp);

}

static SNL explainToSNL(Explain e) {

  if (e == null)

    ret null;

  S c = e.className();

  if (eq(c, "word")) ret new SNL(e.string());

  exp.sub

        else {

      //printStructure(exp.e);

      printTree(0, exp);

    }

}

static void printTree(int indent, Explain e) {

  if (e == null) {

    // this would print "null" for every <identifier> etc

    if (printNulls)

      print(indent(indent) + "null");

  } else {

    print(indent(indent) + e.className() + " | " + quote(e.string()));

    for (Explain sub : e.subs)

      printTree(indent+2, sub);

  }

}