Re: [PATCH 3/4] java: add support for lookahead correction

[Akim Demaille]

> Le 1 nov. 2020 à 19:33, Akim Demaille <akim.demaille@gmail.com> a écrit :
> 
> Shamelessly stolen from Adrian Vogelsgesang's implementation in
> lalr1.cc.
> 
> * data/skeletons/lalr1.java (yycdebugNnl, yyLacCheck, yyLacEstablish)
> (yyLacDiscard, yylacStack, yylacEstablished): New.
> (Context): Use it.
> * examples/java/calc/Calc.y: Enable LAC.

I'll append this patch to the previous one.

commit d15691045342fb67796a1368698ad8ee4c5799b9
Author: Akim Demaille <akim.demaille@gmail.com>
Date:   Tue Nov 3 08:21:35 2020 +0100

    java: prefer ArrayList to Vector
    
    Vector is synchronized, which is completely useless in our case (and
    not even relevant when concurrency matters).  No seasoned Java
    programmer would use it.
    Reported by Uxio Prego.
    
    * data/skeletons/lalr1.java: Replace Vector with ArrayList.
    Unfortunately its API is not as rich, and lacks lastElement and
    setSize.

diff --git a/data/skeletons/lalr1.java b/data/skeletons/lalr1.java
index be2900ef..26508a8c 100644
--- a/data/skeletons/lalr1.java
+++ b/data/skeletons/lalr1.java
@@ -102,7 +102,7 @@ b4_output_begin([b4_parser_file_name])[
 ]b4_user_pre_prologue[
 ]b4_user_post_prologue[
 import java.text.MessageFormat;
-import java.util.Vector;
+import java.util.ArrayList;
 ]b4_percent_code_get([[imports]])[
 /**
  * A Bison parser, automatically generated from 
<tt>]m4_bpatsubst(b4_file_name, [^"\(.*\)"$], [\1])[</tt>.
@@ -268,7 +268,7 @@ import java.util.Vector;
   public 
]b4_parser_class[(]b4_parse_param_decl([b4_lex_param_decl])[)]b4_maybe_throws([b4_init_throws])[
   {
 ]b4_percent_code_get([[init]])[]b4_lac_if([[
-    this.yylacStack = new Vector<Integer>();
+    this.yylacStack = new ArrayList<Integer>();
     this.yylacEstablished = false;]])[
     this.yylexer = new YYLexer(]b4_lex_param_call[);
 ]b4_parse_param_cons[
@@ -282,7 +282,7 @@ import java.util.Vector;
   ]b4_lexer_if([[protected]], [[public]]) 
b4_parser_class[(]b4_parse_param_decl([[Lexer 
yylexer]])[)]b4_maybe_throws([b4_init_throws])[
   {
 ]b4_percent_code_get([[init]])[]b4_lac_if([[
-    this.yylacStack = new Vector<Integer>();
+    this.yylacStack = new ArrayList<Integer>();
     this.yylacEstablished = false;]])[
     this.yylexer = yylexer;
 ]b4_parse_param_cons[
@@ -852,7 +852,7 @@ b4_dollar_popdef[]dnl
     this.yylen = 0;
     this.yystate = 0;
     this.yystack = new YYStack();]b4_lac_if([[
-    this.yylacStack = new Vector<Integer>();
+    this.yylacStack = new ArrayList<Integer>();
     this.yylacEstablished = false;]])[
     this.label = YYNEWSTATE;
 
@@ -1021,7 +1021,7 @@ b4_dollar_popdef[]dnl
         {
           int topState = (yylacStack.isEmpty()
                           ? yystack.stateAt(lacTop)
-                          : yylacStack.lastElement());
+                          : yylacStack.get(yylacStack.size() - 1));
           int yyrule = yypact_[topState];
           if (yyPactValueIsDefault(yyrule)
               || (yyrule += yytoken.getCode()) < 0 || YYLAST_ < yyrule
@@ -1056,7 +1056,10 @@ b4_dollar_popdef[]dnl
             // First pop from the LAC stack as many tokens as possible.
             int lacSize = yylacStack.size();
             if (yylen < lacSize) {
-              yylacStack.setSize(lacSize - yylen);
+              // yylacStack.setSize(lacSize - yylen);
+              for (/* Nothing */; 0 < yylen; yylen -= 1) {
+                yylacStack.remove(yylacStack.size() - 1);
+              }
               yylen = 0;
             } else if (lacSize != 0) {
               yylacStack.clear();
@@ -1069,7 +1072,7 @@ b4_dollar_popdef[]dnl
           // Keep topState in sync with the updated stack.
           topState = (yylacStack.isEmpty()
                       ? yystack.stateAt(lacTop)
-                      : yylacStack.lastElement());
+                      : yylacStack.get(yylacStack.size() - 1));
           // Push the resulting state of the reduction.
           int state = yyLRGotoState(topState, yyr1_[yyrule]);
           yycdebugNnl(" G" + state);
@@ -1139,7 +1142,7 @@ b4_dollar_popdef[]dnl
      * yylacCheck. We just store it as a member of this class to hold
      * on to the memory and to avoid frequent reallocations.
      */
-    Vector<Integer> yylacStack;
+    ArrayList<Integer> yylacStack;
     /**  Whether an initial LAC context was established. */
     boolean yylacEstablished;
 ]])[