From 6c257fc45ba620d547f6b18f55825a727a022f18 Mon Sep 17 00:00:00 2001
From: Richard van Velzen <info@liefcoden.nl>
Date: Thu, 29 Dec 2011 02:04:17 +0100
Subject: [PATCH] Added support for inline %prec definitions

---
 examples/calc.class | 640 +++++++++++++++++++++-----------------------
 examples/calc.lime  |   2 +
 lime.bootstrap      |   4 +
 lime.php            |  48 ++--
 lime_scan_tokens    | Bin 22209 -> 22209 bytes
 lime_scan_tokens.l  |   3 +
 parse_engine.php    |  17 +-
 7 files changed, 367 insertions(+), 347 deletions(-)

diff --git a/examples/calc.class b/examples/calc.class
index cb2f3c5..e1e4dd9 100644
--- a/examples/calc.class
+++ b/examples/calc.class
@@ -1,335 +1,315 @@
 <?php
-
-
 /*
+ *** DON'T EDIT THIS FILE! ***
+ *
+ * This file was automatically generated by the Lime parser generator.
+ * The real source code you should be looking at is in one or more
+ * grammar files in the Lime format.
+ *
+ * THE ONLY REASON TO LOOK AT THIS FILE is to see where in the grammar
+ * file that your error happened, because there are enough comments to
+ * help you debug your grammar.
 
-DON'T EDIT THIS FILE!
-
-This file was automatically generated by the Lime parser generator.
-The real source code you should be looking at is in one or more
-grammar files in the Lime format.
-
-THE ONLY REASON TO LOOK AT THIS FILE is to see where in the grammar
-file that your error happened, because there are enough comments to
-help you debug your grammar.
-
-If you ignore this warning, you're shooting yourself in the brain,
-not the foot.
-
-*/
-
+ * If you ignore this warning, you're shooting yourself in the brain,
+ * not the foot.
+ */
 class calc extends lime_parser {
-var $qi = 0;
-var $i = array (
-  0 => 
-  array (
-    'exp' => 's 1',
-    'var' => 's 15',
-    'num' => 's 3',
-    '\'(\'' => 's 12',
-    'stmt' => 's 18',
-    '\'start\'' => 'a \'start\'',
-  ),
-  1 => 
-  array (
-    '\'+\'' => 's 2',
-    '\'-\'' => 's 6',
-    '\'*\'' => 's 8',
-    '\'/\'' => 's 10',
-    '#' => 'r 0',
-  ),
-  2 => 
-  array (
-    'num' => 's 3',
-    'var' => 's 4',
-    'exp' => 's 5',
-    '\'(\'' => 's 12',
-  ),
-  3 => 
-  array (
-    '\'+\'' => 'r 2',
-    '\'-\'' => 'r 2',
-    '\'*\'' => 'r 2',
-    '\'/\'' => 'r 2',
-    '\')\'' => 'r 2',
-    '#' => 'r 2',
-  ),
-  4 => 
-  array (
-    '\'+\'' => 'r 3',
-    '\'-\'' => 'r 3',
-    '\'*\'' => 'r 3',
-    '\'/\'' => 'r 3',
-    '\')\'' => 'r 3',
-    '#' => 'r 3',
-  ),
-  5 => 
-  array (
-    '\'+\'' => 'r 4',
-    '\'-\'' => 'r 4',
-    '\'*\'' => 's 8',
-    '\'/\'' => 's 10',
-    '\')\'' => 'r 4',
-    '#' => 'r 4',
-  ),
-  6 => 
-  array (
-    'num' => 's 3',
-    'var' => 's 4',
-    'exp' => 's 7',
-    '\'(\'' => 's 12',
-  ),
-  7 => 
-  array (
-    '\'+\'' => 'r 5',
-    '\'-\'' => 'r 5',
-    '\'*\'' => 's 8',
-    '\'/\'' => 's 10',
-    '\')\'' => 'r 5',
-    '#' => 'r 5',
-  ),
-  8 => 
-  array (
-    'num' => 's 3',
-    'var' => 's 4',
-    'exp' => 's 9',
-    '\'(\'' => 's 12',
-  ),
-  9 => 
-  array (
-    '\'+\'' => 'r 6',
-    '\'-\'' => 'r 6',
-    '\'*\'' => 'r 6',
-    '\'/\'' => 'r 6',
-    '\')\'' => 'r 6',
-    '#' => 'r 6',
-  ),
-  10 => 
-  array (
-    'num' => 's 3',
-    'var' => 's 4',
-    'exp' => 's 11',
-    '\'(\'' => 's 12',
-  ),
-  11 => 
-  array (
-    '\'+\'' => 'r 7',
-    '\'-\'' => 'r 7',
-    '\'*\'' => 'r 7',
-    '\'/\'' => 'r 7',
-    '\')\'' => 'r 7',
-    '#' => 'r 7',
-  ),
-  12 => 
-  array (
-    'num' => 's 3',
-    'var' => 's 4',
-    'exp' => 's 13',
-    '\'(\'' => 's 12',
-  ),
-  13 => 
-  array (
-    '\'+\'' => 's 2',
-    '\'-\'' => 's 6',
-    '\'*\'' => 's 8',
-    '\'/\'' => 's 10',
-    '\')\'' => 's 14',
-  ),
-  14 => 
-  array (
-    '\'/\'' => 'r 8',
-    '\'*\'' => 'r 8',
-    '\'-\'' => 'r 8',
-    '\'+\'' => 'r 8',
-    '\')\'' => 'r 8',
-    '#' => 'r 8',
-  ),
-  15 => 
-  array (
-    '\'=\'' => 's 16',
-    '\'+\'' => 'r 3',
-    '\'-\'' => 'r 3',
-    '\'*\'' => 'r 3',
-    '\'/\'' => 'r 3',
-    '#' => 'r 3',
-  ),
-  16 => 
-  array (
-    'exp' => 's 17',
-    'num' => 's 3',
-    'var' => 's 4',
-    '\'(\'' => 's 12',
-  ),
-  17 => 
-  array (
-    '\'+\'' => 's 2',
-    '\'-\'' => 's 6',
-    '\'*\'' => 's 8',
-    '\'/\'' => 's 10',
-    '#' => 'r 1',
-  ),
-  18 => 
-  array (
-    '#' => 'r 9',
-  ),
-);
-function reduce_0_stmt_1($tokens, &$result) {
-#
-# (0) stmt :=  exp
-#
-$result = reset($tokens);
- echo " -> "; echo $tokens[0]; echo "\n"; 
-}
-
-function reduce_1_stmt_2($tokens, &$result) {
-#
-# (1) stmt :=  var  '='  exp
-#
-$result = reset($tokens);
-$v =& $tokens[0];
-$e =& $tokens[2];
-
-	echo "$v = $e\n";
-	set_variable($v, $e);
-
-}
-
-function reduce_2_exp_1($tokens, &$result) {
-#
-# (2) exp :=  num
-#
-$result = reset($tokens);
-
-}
-
-function reduce_3_exp_2($tokens, &$result) {
-#
-# (3) exp :=  var
-#
-$result = reset($tokens);
- $result = get_variable($tokens[0]); 
-}
-
-function reduce_4_exp_3($tokens, &$result) {
-#
-# (4) exp :=  exp  '+'  exp
-#
-$result = reset($tokens);
- $result = $tokens[0] + $tokens[2]; 
-}
-
-function reduce_5_exp_4($tokens, &$result) {
-#
-# (5) exp :=  exp  '-'  exp
-#
-$result = reset($tokens);
- $result = $tokens[0] - $tokens[2]; 
-}
-
-function reduce_6_exp_5($tokens, &$result) {
-#
-# (6) exp :=  exp  '*'  exp
-#
-$result = reset($tokens);
- $result = $tokens[0] * $tokens[2]; 
-}
-
-function reduce_7_exp_6($tokens, &$result) {
-#
-# (7) exp :=  exp  '/'  exp
-#
-$result = reset($tokens);
- $result = $tokens[0] / $tokens[2]; 
-}
-
-function reduce_8_exp_7($tokens, &$result) {
-#
-# (8) exp :=  '('  exp  ')'
-#
-$result = $tokens[1];
-
-}
-
-function reduce_9_start_1($tokens, &$result) {
-#
-# (9) 'start' :=  stmt
-#
-$result = reset($tokens);
-
-}
-
-var $method = array (
-  0 => 'reduce_0_stmt_1',
-  1 => 'reduce_1_stmt_2',
-  2 => 'reduce_2_exp_1',
-  3 => 'reduce_3_exp_2',
-  4 => 'reduce_4_exp_3',
-  5 => 'reduce_5_exp_4',
-  6 => 'reduce_6_exp_5',
-  7 => 'reduce_7_exp_6',
-  8 => 'reduce_8_exp_7',
-  9 => 'reduce_9_start_1',
-);
-var $a = array (
-  0 => 
-  array (
-    'symbol' => 'stmt',
-    'len' => 1,
-    'replace' => true,
-  ),
-  1 => 
-  array (
-    'symbol' => 'stmt',
-    'len' => 3,
-    'replace' => true,
-  ),
-  2 => 
-  array (
-    'symbol' => 'exp',
-    'len' => 1,
-    'replace' => true,
-  ),
-  3 => 
-  array (
-    'symbol' => 'exp',
-    'len' => 1,
-    'replace' => true,
-  ),
-  4 => 
-  array (
-    'symbol' => 'exp',
-    'len' => 3,
-    'replace' => true,
-  ),
-  5 => 
-  array (
-    'symbol' => 'exp',
-    'len' => 3,
-    'replace' => true,
-  ),
-  6 => 
-  array (
-    'symbol' => 'exp',
-    'len' => 3,
-    'replace' => true,
-  ),
-  7 => 
-  array (
-    'symbol' => 'exp',
-    'len' => 3,
-    'replace' => true,
-  ),
-  8 => 
-  array (
-    'symbol' => 'exp',
-    'len' => 3,
-    'replace' => true,
-  ),
-  9 => 
-  array (
-    'symbol' => '\'start\'',
-    'len' => 1,
-    'replace' => true,
-  ),
-);
+  public $qi = 0;
+  public $i = array(
+    array(
+      'exp' => 's 1',
+      'var' => 's 17',
+      'num' => 's 3',
+      "'('" => 's 14',
+      'stmt' => 's 20',
+      "'start'" => "a 'start'"
+    ),
+    array(
+      "'+'" => 's 2',
+      "'-'" => 's 6',
+      "'*'" => 's 8',
+      "'/'" => 's 10',
+      "'^'" => 's 12',
+      '#' => 'r 0'
+    ),
+    array(
+      'num' => 's 3',
+      'var' => 's 4',
+      'exp' => 's 5',
+      "'('" => 's 14'
+    ),
+    array(
+      "'+'" => 'r 2',
+      "'-'" => 'r 2',
+      "'*'" => 'r 2',
+      "'/'" => 'r 2',
+      "'^'" => 'r 2',
+      "')'" => 'r 2',
+      '#' => 'r 2'
+    ),
+    array(
+      "'+'" => 'r 3',
+      "'-'" => 'r 3',
+      "'*'" => 'r 3',
+      "'/'" => 'r 3',
+      "'^'" => 'r 3',
+      "')'" => 'r 3',
+      '#' => 'r 3'
+    ),
+    array(
+      "'+'" => 'r 4',
+      "'-'" => 'r 4',
+      "'*'" => 's 8',
+      "'/'" => 's 10',
+      "'^'" => 's 12',
+      "')'" => 'r 4',
+      '#' => 'r 4'
+    ),
+    array(
+      'num' => 's 3',
+      'var' => 's 4',
+      'exp' => 's 7',
+      "'('" => 's 14'
+    ),
+    array(
+      "'+'" => 'r 5',
+      "'-'" => 'r 5',
+      "'*'" => 's 8',
+      "'/'" => 's 10',
+      "'^'" => 's 12',
+      "')'" => 'r 5',
+      '#' => 'r 5'
+    ),
+    array(
+      'num' => 's 3',
+      'var' => 's 4',
+      'exp' => 's 9',
+      "'('" => 's 14'
+    ),
+    array(
+      "'+'" => 'r 6',
+      "'-'" => 'r 6',
+      "'*'" => 'r 6',
+      "'/'" => 'r 6',
+      "'^'" => 's 12',
+      "')'" => 'r 6',
+      '#' => 'r 6'
+    ),
+    array(
+      'num' => 's 3',
+      'var' => 's 4',
+      'exp' => 's 11',
+      "'('" => 's 14'
+    ),
+    array(
+      "'+'" => 'r 7',
+      "'-'" => 'r 7',
+      "'*'" => 'r 7',
+      "'/'" => 'r 7',
+      "'^'" => 's 12',
+      "')'" => 'r 7',
+      '#' => 'r 7'
+    ),
+    array(
+      'num' => 's 3',
+      'var' => 's 4',
+      'exp' => 's 13',
+      "'('" => 's 14'
+    ),
+    array(
+      "'+'" => 'r 8',
+      "'-'" => 'r 8',
+      "'*'" => 'r 8',
+      "'/'" => 'r 8',
+      "'^'" => 's 12',
+      "')'" => 'r 8',
+      '#' => 'r 8'
+    ),
+    array(
+      'num' => 's 3',
+      'var' => 's 4',
+      'exp' => 's 15',
+      "'('" => 's 14'
+    ),
+    array(
+      "'+'" => 's 2',
+      "'-'" => 's 6',
+      "'*'" => 's 8',
+      "'/'" => 's 10',
+      "'^'" => 's 12',
+      "')'" => 's 16'
+    ),
+    array(
+      "'^'" => 'r 9',
+      "'/'" => 'r 9',
+      "'*'" => 'r 9',
+      "'-'" => 'r 9',
+      "'+'" => 'r 9',
+      "')'" => 'r 9',
+      '#' => 'r 9'
+    ),
+    array(
+      "'='" => 's 18',
+      "'+'" => 'r 3',
+      "'-'" => 'r 3',
+      "'*'" => 'r 3',
+      "'/'" => 'r 3',
+      "'^'" => 'r 3',
+      '#' => 'r 3'
+    ),
+    array(
+      'exp' => 's 19',
+      'num' => 's 3',
+      'var' => 's 4',
+      "'('" => 's 14'
+    ),
+    array(
+      "'+'" => 's 2',
+      "'-'" => 's 6',
+      "'*'" => 's 8',
+      "'/'" => 's 10',
+      "'^'" => 's 12',
+      '#' => 'r 1'
+    ),
+    array(
+      '#' => 'r 10'
+    )
+  );
+  function reduce_0_stmt_1($tokens, &$result) {
+    // (0) stmt :=  exp
+    $result = reset($tokens);
+    echo " -> "; echo $tokens[0]; echo "\n";
+  }
+
+  function reduce_1_stmt_2($tokens, &$result) {
+    // (1) stmt :=  var  '='  exp
+    $result = reset($tokens);
+    $v = &$tokens[0];
+    $e = &$tokens[2];
+
+    echo "$v = $e\n";
+    set_variable($v, $e);
+  }
+
+  function reduce_2_exp_1($tokens, &$result) {
+    // (2) exp :=  num
+    $result = reset($tokens);
+  }
+
+  function reduce_3_exp_2($tokens, &$result) {
+    // (3) exp :=  var
+    $result = reset($tokens);
+    $result = get_variable($tokens[0]);
+  }
+
+  function reduce_4_exp_3($tokens, &$result) {
+    // (4) exp :=  exp  '+'  exp
+    $result = reset($tokens);
+    $result = $tokens[0] + $tokens[2];
+  }
+
+  function reduce_5_exp_4($tokens, &$result) {
+    // (5) exp :=  exp  '-'  exp
+    $result = reset($tokens);
+    $result = $tokens[0] - $tokens[2];
+  }
+
+  function reduce_6_exp_5($tokens, &$result) {
+    // (6) exp :=  exp  '*'  exp
+    $result = reset($tokens);
+    $result = $tokens[0] * $tokens[2];
+  }
+
+  function reduce_7_exp_6($tokens, &$result) {
+    // (7) exp :=  exp  '/'  exp
+    $result = reset($tokens);
+    $result = $tokens[0] / $tokens[2];
+  }
+
+  function reduce_8_exp_7($tokens, &$result) {
+    // (8) exp :=  exp  '^'  exp
+    $result = reset($tokens);
+    $result = pow($tokens[0], $tokens[2]);
+  }
+
+  function reduce_9_exp_8($tokens, &$result) {
+    // (9) exp :=  '('  exp  ')'
+    $result = $tokens[1];
+  }
+
+  function reduce_10_start_1($tokens, &$result) {
+    // (10) 'start' :=  stmt
+    $result = reset($tokens);
+  }
+
+  public $method = array(
+    'reduce_0_stmt_1',
+    'reduce_1_stmt_2',
+    'reduce_2_exp_1',
+    'reduce_3_exp_2',
+    'reduce_4_exp_3',
+    'reduce_5_exp_4',
+    'reduce_6_exp_5',
+    'reduce_7_exp_6',
+    'reduce_8_exp_7',
+    'reduce_9_exp_8',
+    'reduce_10_start_1'
+  );
+  public $a = array(
+    array(
+      'symbol' => 'stmt',
+      'len' => 1,
+      'replace' => true
+    ),
+    array(
+      'symbol' => 'stmt',
+      'len' => 3,
+      'replace' => true
+    ),
+    array(
+      'symbol' => 'exp',
+      'len' => 1,
+      'replace' => true
+    ),
+    array(
+      'symbol' => 'exp',
+      'len' => 1,
+      'replace' => true
+    ),
+    array(
+      'symbol' => 'exp',
+      'len' => 3,
+      'replace' => true
+    ),
+    array(
+      'symbol' => 'exp',
+      'len' => 3,
+      'replace' => true
+    ),
+    array(
+      'symbol' => 'exp',
+      'len' => 3,
+      'replace' => true
+    ),
+    array(
+      'symbol' => 'exp',
+      'len' => 3,
+      'replace' => true
+    ),
+    array(
+      'symbol' => 'exp',
+      'len' => 3,
+      'replace' => true
+    ),
+    array(
+      'symbol' => 'exp',
+      'len' => 3,
+      'replace' => true
+    ),
+    array(
+      'symbol' => "'start'",
+      'len' => 1,
+      'replace' => true
+    )
+  );
 }
diff --git a/examples/calc.lime b/examples/calc.lime
index d55deb1..984c4ad 100644
--- a/examples/calc.lime
+++ b/examples/calc.lime
@@ -3,6 +3,7 @@
 
 %left '+' '-'
 %left '*' '/'
+%right '^'
 
 stmt = exp { echo " -> "; echo $1; echo "\n"; }
 | var/v '=' exp/e {
@@ -18,6 +19,7 @@ exp = num
 | exp '-' exp { $$ = $1 - $3; }
 | exp '*' exp { $$ = $1 * $3; }
 | exp '/' exp { $$ = $1 / $3; }
+| exp '^' exp { $$ = pow($1, $3); }
 | '(' exp/$ ')'
 .
 
diff --git a/lime.bootstrap b/lime.bootstrap
index 63791c7..1730b64 100644
--- a/lime.bootstrap
+++ b/lime.bootstrap
@@ -22,6 +22,7 @@ lit : $$ = new lime_glyph($1, NULL);
 to slot
 : $$ = new lime_rhs();
 rhs slot : $$->add($2);
+rhs prec tok : $$->set_prec_glyph($3);
 to rhs
 '{' code '}' : $$ = $2;
 to action
@@ -29,3 +30,6 @@ to action
 code php : $$.=$2;
 code '{' code '}' : $$.='{'.$3.'}';
 to code
+sym :
+lit :
+to tok
diff --git a/lime.php b/lime.php
index 7f9eb6f..085023f 100755
--- a/lime.php
+++ b/lime.php
@@ -160,11 +160,13 @@ class error extends step {
 
 class shift extends step {
 	public $q;
+	public $rule;
 
-	public function __construct(sym $sym, $q) {
+	public function __construct(sym $sym, $q, rule $rule) {
 		parent::__construct($sym);
 
 		$this->q = $q;
+		$this->rule = $rule;
 	}
 
 	public function instruction() {
@@ -178,7 +180,7 @@ class shift extends step {
 		bug_unless($that instanceof reduce);
 
 		// That being said, the resolution is a matter of precedence.
-		$shift_prec = $this->sym->right_prec;
+		$shift_prec = $this->rule->right_prec;
 		$reduce_prec = $that->rule->prec;
 
 		// If we don't have defined precedence levels for both options,
@@ -274,8 +276,8 @@ class state {
 		}
 	}
 
-	public function add_shift(sym $sym, $state) {
-		$this->add_instruction(new shift($sym, $state->id));
+	public function add_shift(sym $sym, $state, $rule) {
+		$this->add_instruction(new shift($sym, $state->id, $rule));
 	}
 
 	public function add_reduce(sym $sym, $rule) {
@@ -375,7 +377,7 @@ class sym {
 }
 
 class rule {
-	public function __construct($id, $sym, $rhs, $code, $look, $replace) {
+	public function __construct($id, $sym, $rhs, $code, $look, $replace, $prec_sym) {
 		bug_unless(is_int($look));
 
 		$this->id = $id;
@@ -384,8 +386,9 @@ class rule {
 		$this->code = $code;
 		$this->look = $look;
 		$this->replace = $replace;
-		//$this->prec_sym = $prec_sym;
+		$this->prec_sym = $prec_sym;
 		$this->prec = 0;
+		$this->right_prec = 0;
 		$this->first = array();
 		$this->epsilon = count($rhs);
 	}
@@ -401,15 +404,17 @@ class rule {
 		// is a reasonable alternative behaviour, but I don't see the big
 		// deal just now.
 
-		//$prec_sym = $this->prec_sym;
-		//if (!$prec_sym)
-		$prec_sym = $this->rightmost_terminal();
+		$prec_sym = $this->prec_sym;
+		if (!$prec_sym) {
+			$prec_sym = $this->rightmost_terminal();
+		}
 
 		if (!$prec_sym) {
 			return;
 		}
 
 		$this->prec = $prec_sym->left_prec;
+		$this->right_prec = $prec_sym->right_prec;
 	}
 
 	private function rightmost_terminal() {
@@ -664,7 +669,7 @@ class lime {
 		return "'{$real}'" . count($this->rule);
 	}
 
-	function add_raw_rule($lhs, $rhs, $code, $look, $replace) {
+	function add_raw_rule($lhs, $rhs, $code, $look, $replace, $prec_sym) {
 		$sym = $this->sym($lhs);
 		$sym->term = false;
 
@@ -679,7 +684,7 @@ class lime {
 		}
 
 		$rid = count($this->rule);
-		$r = new rule($rid, $sym, $rs, $code, $look, $replace);
+		$r = new rule($rid, $sym, $rs, $code, $look, $replace, $prec_sym);
 		$this->rule[$rid] = $r;
 		$sym->rule[] = $r;
 	}
@@ -754,7 +759,7 @@ class lime {
 		$candidate = current($this->start_symbol_set);
 
 		// Did the person try to set a start symbol at all?
-		if (!$candidate) {
+		if (!is_object($candidate)) {
 			return $this->first_rule_lhs();
 		}
 
@@ -862,7 +867,7 @@ class lime {
 			}
 
 			$dest = $this->get_state($basis);
-			$state->add_shift($this->sym($glyph), $dest);
+			$state->add_shift($this->sym($glyph), $dest, $segment[0]->rule);
 		}
 	}
 
@@ -1074,6 +1079,8 @@ class lime_language_php extends lime_language {
 }
 
 class lime_rhs {
+	public $prec_glyph;
+
 	function __construct() {
 		// Construct and add glyphs and actions in whatever order.
 		// Then, add this to a lime_rewrite.
@@ -1083,10 +1090,14 @@ class lime_rhs {
 		$this->rhs = array();
 	}
 
-	function add(lime_slot $slot) {
+	public function add(lime_slot $slot) {
 		$this->rhs[] = $slot;
 	}
 
+	public function set_prec_glyph($glyph) {
+		$this->prec_glyph = $glyph;
+	}
+
 	function install_rule(lime $lime, $lhs) {
 		// This is the part that has to break the rule into subrules if necessary.
 		$rhs = $this->rhs;
@@ -1095,6 +1106,11 @@ class lime_rhs {
 			$rhs[] = new lime_action('', null);
 		}
 
+		$prec_sym = null;
+		if ($this->prec_glyph) {
+			$prec_sym = $lime->sym($this->prec_glyph);
+		}
+
 		// Now, split it into chunks based on the actions.
 
 		$lang = $lime->language();
@@ -1118,12 +1134,12 @@ class lime_rhs {
 					// no.
 					$subsymbol = $lime->trump_up_bogus_lhs($lhs);
 					$action = $lang->default_result() . $preamble . $code;
-					$lime->add_raw_rule($subsymbol, $subrule, $action, $look, false);
+					$lime->add_raw_rule($subsymbol, $subrule, $action, $look, false, $prec_sym);
 					$subrule = array($subsymbol);
 				} else {
 					// yes.
 					$action = $result_code . $preamble . $code;
-					$lime->add_raw_rule($lhs, $subrule, $action, $look, true);
+					$lime->add_raw_rule($lhs, $subrule, $action, $look, true, $prec_sym);
 				}
 			} else {
 				impossible();
diff --git a/lime_scan_tokens b/lime_scan_tokens
index 70c7e0c9b2f03af77b11da064f371d9cd451d5c2..bb2b32765071218e3553a851b45389cbaee3cd0b 100755
GIT binary patch
delta 4416
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BVkQ6p

diff --git a/lime_scan_tokens.l b/lime_scan_tokens.l
index d8d9a9d..9cd0586 100644
--- a/lime_scan_tokens.l
+++ b/lime_scan_tokens.l
@@ -63,6 +63,9 @@ BLOCKCMT	"/*"({CC}|{CX})*{CT}
 {BLOCKCMT}		{}
 "/"{WORD}+ |
 "/$"			out("lambda", yytext+1);
+"%prec"			{
+	tok("prec");
+}
 "%"{WORD}+ 		{
 	out("pragma", yytext+1);
 	yy_push_state(pragma);
diff --git a/parse_engine.php b/parse_engine.php
index 587c56e..f30b718 100644
--- a/parse_engine.php
+++ b/parse_engine.php
@@ -260,6 +260,18 @@ class parse_engine {
 		return explode(' ', $row[$type]);
 	}
 
+	private function get_steps() {
+		$out = array();
+		foreach($this->current_row() as $type => $row) {
+			list($opcode) = explode(' ', $row, 2);
+			if ($opcode != 'e') {
+				$out[] = $type;
+			}
+		}
+
+		return $out;
+	}
+
 	private function has_step_for($type) {
 		$row = $this->current_row();
 		return isset($row[$type]);
@@ -300,6 +312,9 @@ class parse_engine {
 			// flutter while the parse engine waits for an edible token.
 			// if ($this->debug) echo "($type) causes a problem.\n";
 
+			// get these before doing anything
+			$expected = $this->get_steps();
+
 			if ($this->enter_error_tolerant_state()) {
 				$this->eat('error', null);
 				if ($this->has_step_for($type)) {
@@ -307,7 +322,7 @@ class parse_engine {
 				}
 			} else {
 				// If that didn't work, give up:
-				throw new parse_error("Parse Error: ({$type})({$semantic}) not expected");
+				throw new parse_error("Parse Error: ({$type})({$semantic}) not expected, expected {" . implode(', ', $expected) . '}');
 			}
 			break;
 		default: