In C$++$ Please

Private member elements:

A vector of structs named symbolTable where the struct contains $2$ fields: name $($type

string$)$ and value $($type double$).$

Methods $-$ Implement the following functions:

Implement the makeExpTree functions that accepts an exp as a string argument and

create expTree.

A bool function named readSymbol that accepts a filename $($string$)$ as argument and read

data from a file where each row has two values: a symbol name $($string$)$ and a value

$($double$).$ Function heading:

bool readSymbol $($string fname$)$

Function return true if file is opened successfully, false otherwise.

A lookup function that accepts two arguments: string and value as show below:

bool lookup $($string name, double & value$)$

function find the value from the symbolTable matching that of the given name. It return

false if the name is not found in the table.

A double function named eval that evaluates the expression tree and assign result to the

reference argument. This evaluation should handle expression with a mix of numbers $($in

string form$)$ and variables whose value can be found in symbolTable. Function heading:

bool eval $($double & result$)$;

function return the true if eval is successful, false otherwise. For this assignment, we will

assume that the expression is grammatically correct. As such, the only error will be the

result of missing symbol which is identified by the lookup function. A straightforward

implementation is to call a recursive version of the eval function that does all the work. It

will have the following heading:

bool eval$($node $$ string$*rt,$ double& result$)$;

Sample I$/$O

Create an appropriate main function that will test all the new features. For example, the main

could first read the data from a file by calling readSymbol. It then continue to ask user for infix

expression, create an exp tree and then call eval to evaluate and print the result.

Required Data Structure

You MUST use ExpTree class which derives from binary tree base class.