I managed to confuse myself pretty well.

I'm doing some reading up on LR(n) parsers, I just sort of started without
thinking about it this time, not a great approach.  I feel like it can't hurt
to have an update on how this works anyway.  I think the idea was solid, but
I was trying to do too much at once.

One question is what my goal should be for this.  I could just solve the
equation as we go, or I could generate code that will let us solve the equation.

The later is obviously attractive in that it will let us run an expression
more than once, and maybe even define functions.  I like that.

1 files changed, 31 insertions, 3 deletions

diff --git a/src/parser.cpp b/src/parser.cpp
index 1f9a193..0131ba3 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -23,25 +23,53 @@ void Parser::parse()
     for(;;)

     {

         lex.nextToken();

+        if( lex[0].eType == Token::tEndOfInput )

+            break;

+

         expr();

 

+        Bu::sio << "Final stack:";

         for( TokenStack::iterator i = tsStack.begin(); i; i++ )

         {

-            Bu::sio << *i << " ";

+            Bu::sio << " " << (*i).eType;

+            if( (*i).eType == Token::tNumber )

+            {

+                Bu::sio << "(" << (*i).nVal->toString() << ")";

+            }

         }

+        Bu::sio << Bu::sio.nl;

     }

 }

 

 void Parser::expr()

 {

+    if( lex[0].eType == Token::tEndOfInput )

+        return;

     if( lex[0].eType == Token::tVariable &&

         lex[1].eType == Token::tEquals )

     {

-        // Assignment!

+        Token t = lex[0];

+        lex.nextToken();

+        lex.nextToken();

         expr();

+

         return;

     }

     exprP();

+

+    switch( lex[0].eType )

+    {

+        case Token::tPlus:

+        case Token::tMinus:

+        case Token::tMultiply:

+        case Token::tDivide:

+        case Token::tModulus:

+            Token t = lex[0];

+            lex.nextToken();

+            expr();

+            tsStack.push( t );

+            break;

+    }

 }

 

 void Parser::exprP()

@@ -222,7 +250,7 @@ void Parser::setVariable( const Bu::String &sName, const Number &rValue )
     hVars.insert( sName, rValue );

 }

 

-void Parser::unwind()

+void Parser::reduce()

 {

     /*

     for(;;)