From c208b397b798910df4ad129fb13d562b4450034e Mon Sep 17 00:00:00 2001
From: Mike Buland <eichlan@xagasoft.com>
Date: Mon, 19 Feb 2007 05:15:23 +0000
Subject: The formula system works just fine, just no functions yet, but I
 don't need them for quite a while.

---
 src/formula.h | 59 +++++++++++++++++++++++++++++++++++++----------------------
 1 file changed, 37 insertions(+), 22 deletions(-)

(limited to 'src/formula.h')

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
-- 
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