Understanding C++ Expression Templates - Angelika Langer

28First attemptDefine the creator functions as overloaded operators:template BinaryExpr operator+(ExprT1 e1, ExprT2 e2){ return BinaryExpr (e1,e2); }An expression such as x+2 would evaluate toBinaryExpr (x,2)which is not exactly what we need. From just the type thecompiler cannot distinguish between a literal and a variableof type double. We need an binary expression that stores aVariable and a Literal expression internally.© Copyright 1995-2000 by Angelika Langer. All Rights Reserved.http://www.AngelikaLanger.com(55)last update: 11/7/2005 ,21:37Define variables as Variable expressions:double x; Variable v(x);cout