Program in C++

Consider the following BNF grammar:

A -> I = E | E E -> P O P | P O -> + | - | * | / | ** P -> I | L | UI | UL | (E) U -> + | - | ! I -> C | CI C -> a | b | ... | y | z L -> D | DL D -> 0 | 1 | ... | 8 | 9 

Using the technique described in class implement a recursive descent parser that recognizes strings in this language. Input should be from a file called input.txt and output should be to the console. An example session might look like this (these strings are not necessarily in the language):

String read from file: a=a+b-c*d The string "a=a+b-c*d" is in the language. String read from file: a=a//b++c The string "a=a//b++c" is not in the language.