added error.h

error.h

@@ -0,0 +1,40 @@
+#ifndef _ERROR_H
+#define _ERROR_H
+
+#include <exception>
+#include <sstream>
+
+namespace ledger {
+
+class error : public std::exception
+{
+  std::string reason;
+ public:
+  error(const std::string& _reason) throw() : reason(_reason) {}
+  virtual ~error() throw() {}
+
+  virtual const char* what() const throw() {
+    return reason;
+  }
+};
+
+class parse_error : public error
+{
+  unsigned int line;
+  std::string  file;
+ public:
+  parse_error(const std::string& _file, const unsigned int _line,
+	      const std::string& reason) throw()
+    : line(_line), file(_file), error(reason) {}
+  virtual ~parse_error() throw() {}
+
+  virtual const char* what() const throw() {
+    static std::ostringstream msg;
+    msg << "Error: " << file << ", line " << line << ": " << error::what();
+    return msg.str().c_str();
+  }
+};
+
+} // namespace ledger
+
+#endif // _CONSTRAINT_H