1 files changed, 37 insertions, 22 deletions

diff --git a/src/formula.h b/src/formula.h
index 1eccd36..939eb09 100644
--- a/src/formula.h
+++ b/src/formula.h
@@ -3,15 +3,19 @@
 
 #include <stdint.h>
 
+#include <math.h>
 #include <stack>
 #include "sbuffer.h"
 
 #include "exceptionbase.h"
+#include "hash.h"
 
 subExceptionDecl( ParseException );
 
 /**
- *
+ * Implements a very simple formula parser that allows use of variables and
+ * custom functions.  This is based on a simple calculator-type parser that
+ * executes as it processes, accounting for operator precedence and grouping.
  */
 class Formula
 {
@@ -19,7 +23,29 @@ public:
         Formula();
         virtual ~Formula();
 
-        double run( const char *sFormula );
+        double run( char *sFormula );
+
+        typedef Hash<std::string, double> varHash;
+        varHash hVars;
+
+        typedef struct Func
+        {
+                double operator()( double x )
+                {
+                        return 0.0;
+                }
+        } Func;
+
+        typedef Hash<std::string, Func> funcHash;
+        funcHash hFunc;
+
+        typedef struct FuncSin : Func
+        {
+                double operator()( double x )
+                {
+                        return sin( x );
+                }
+        } FuncSin;
 
 private:
         enum
@@ -32,31 +58,20 @@ private:
                 symOpenParen,
                 symCloseParen,
                 symNumber,
-                symVariable
+                symVariable,
+                symExponent,
+                symModulus
         };
 
-        typedef struct Token
-        {
-                Token() {}
-                Token( uint8_t nSym ) : nSym( nSym ) { }
-                Token( uint8_t nSym, double dNum ) : nSym( nSym ) { val.num = dNum; }
-                uint8_t nSym;
-                union 
-                {
-                        double num;
-                } val;
-        } Token;
+        typedef uint8_t symType;
 
-        std::stack<Token> sToken;
-        Token tLook;
-        int nState;
-        SBuffer sBuf;
+        std::stack<symType> sOper;
+        std::stack<double> sValue;
 
 private:
-        void push();
-        void state();
-        Token nextToken();
-        void printToken( Token &tok );
+        symType getPrec( symType nOper );
+        symType nextToken( char **sBuf );
+        void reduce( bool bCloseParen = false );
 };
 
 #endif