diff --git a/str2num.h b/str2num.h
new file mode 100644
index 0000000..6f86c8c
--- /dev/null
+++ b/str2num.h
@@ -0,0 +1,60 @@
+#ifndef __STR2NUM_H__
+#define __STR2NUM_H__
+
+#include <iostream>
+#include <cstring>
+
+namespace nasal
+{
+
+void Str2Num(std::string &str)
+{
+	for(int i=0;i<(int)str.length();++i)
+		if(!(('0'<=str[i]) && (str[i]<='9') || (str[i]=='.')))
+		{
+			std::cout<<"[Error] Non-numeric string."<<std::endl;
+			return;
+		}
+	
+	bool isFloat=false;
+	int DotPlace=0;
+	for(int i=0;i<(int)str.length();++i)
+		if(str[i]=='.')
+		{
+			isFloat=true;
+			DotPlace=i;
+			break;
+		}
+	if(!isFloat)
+	{
+		long long int num=0;
+		long long int acc=1;
+		for(int i=(int)str.length()-1;i>=0;--i)
+		{
+			num+=acc*((long long int)(str[i]-'0'));
+			acc*=10;
+		}
+		std::cout<<num<<std::endl;
+	}
+	else
+	{
+		double num=0;
+		double acc=1;
+		double aff=0.1;
+		for(int i=DotPlace+1;i<(int)str.length();++i)
+		{
+			num+=aff*((double)(str[i]-'0'));
+			aff*=0.1;
+		}
+		for(int i=DotPlace-1;i>=0;--i)
+		{
+			num+=acc*((double)(str[i]-'0'));
+			acc*=10;
+		}
+		std::cout<<num<<std::endl;
+	}
+	return;
+}
+
+}
+#endif