From 89eeeff54f0b3ce30be5b046fc3899fdeb5ebb40 Mon Sep 17 00:00:00 2001
From: Mike Buland <eichlan@xagasoft.com>
Date: Sat, 17 Feb 2007 16:31:55 +0000
Subject: Tweaked the stream classes, added an example, and the begining of a
 formula parser.

---
 src/formula.cpp | 157 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 157 insertions(+)
 create mode 100644 src/formula.cpp

(limited to 'src/formula.cpp')

diff --git a/src/formula.cpp b/src/formula.cpp
new file mode 100644
index 0000000..7cc1804
--- /dev/null
+++ b/src/formula.cpp
@@ -0,0 +1,157 @@
+#include "formula.h"
+
+subExceptionDef( ParseException );
+
+Formula::Formula()
+{
+}
+
+Formula::~Formula()
+{
+}
+
+double Formula::run( const char *sFormula )
+{
+	sBuf.write( sFormula, strlen( sFormula ) );
+	sBuf.setPos( 0 );
+
+	nState = 0;
+	for(;;)
+	{
+		tLook = nextToken();
+		if( tLook.nSym == symEOS )
+			break;
+		state();
+	}
+	printf("\n");
+	return 0.0;
+}
+
+void Formula::state()
+{
+	switch( nState )
+	{
+		case 0: // initial expr
+			switch( tLook.nSym )
+			{
+				case symNumber:
+					push();
+					nState = 1;
+					break;
+			}
+			break;
+
+		case 1: // binary operator
+			switch( tLook.nSym )
+			{
+				case symAdd:
+				case symSubtract:
+					push();
+					nState = 2;
+					break;
+
+				case symMultiply:
+				case symDivide:
+					push();
+					nState = 3;
+					break;
+			}
+			break;
+
+		case 2: // add/subtract
+			break;
+	}
+}
+
+void Formula::push()
+{
+	printToken( tLook );
+	sToken.push( tLook );
+}
+
+Formula::Token Formula::nextToken()
+{
+	char cbuf;
+	for(;;)
+	{
+		if( sBuf.isEOS() )
+			return Token( symEOS );
+
+		sBuf.read( &cbuf, 1 );
+		switch( cbuf )
+		{
+			case '+':
+				return Token( symAdd );
+
+			case '-':
+				return Token( symSubtract );
+
+			case '*':
+				return Token( symMultiply );
+
+			case '/':
+				return Token( symDivide );
+
+			case '(':
+				return Token( symOpenParen );
+
+			case ')':
+				return Token( symCloseParen );
+
+			case ' ':
+			case '\t':
+			case '\n':
+			case '\r':
+				break;
+
+			default:
+				if( cbuf == '.' || (cbuf >= '0' && cbuf <= '9') )
+				{
+					char num[50];
+					int nPos = 0;
+					bool bDot = false;
+
+					for(;;)
+					{
+						num[nPos++] = cbuf;
+						if( cbuf == '.' )
+						{
+							if( bDot == false )
+								bDot = true;
+							else
+								throw ParseException(
+									"Numbers cannot have more than one "
+									". in them."
+									);
+						}
+						sBuf.read( &cbuf, 1 );
+						if( (cbuf != '.' && (cbuf < '0' || cbuf > '9')) || 
+							sBuf.isEOS() )
+						{
+							if( !sBuf.isEOS() )	sBuf.seek( -1 );
+							num[nPos] = '\0';
+							return Token( symNumber, strtod( num, NULL ) );
+						}
+					}
+				}
+				break;
+		}
+	}
+}
+
+void Formula::printToken( Token &tok )
+{
+	switch( tok.nSym )
+	{
+		case symEOS:		printf("[EOS] ");				break;
+		case symAdd:		printf("+ ");					break;
+		case symSubtract:	printf("- ");					break;
+		case symMultiply:	printf("* ");					break;
+		case symDivide:		printf("/ ");					break;
+		case symOpenParen:	printf("( ");					break;
+		case symCloseParen:	printf(") ");					break;
+		case symNumber:		printf("%f ", tok.val.num );	break;
+		default:			printf("??? ");					break;
+	}
+}
+
-- 
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