Introduction
ATL stands for Active Template Library, developed by Microsoft. The purpose of ATL is to simplify the program based on the Component Object Model (COM ). An ATL contains a set of C++ template classes to develop efficient COM objects.

In this blog, we will discuss the Parse trees in ATL and why we need Parse trees in ATL.
But before this, let's talk about the structure of parse trees.
Structure of Parse Trees
A parser tree represents the symbols that are terminal or non-terminal. A parse tree displays the syntactic structure of a string concerning context-free Grammar.
Non-terminal symbols are those symbols responsible for the creation of the sentence but are not present in the sentence. The terminal symbols are those characters or alphabets in a string generated with the grammar.
A parse tree shows an in-memory representation of the data with a structure that has proper grammar meaning. The tree data structure indicates the hierarchical relation between the nodes or data.
The parse tree is based on the precedence of operators. First, we will traverse the deepest sub-tree. As a result, the parent node operator has lower priority than the sub-tree operator.
A parse tree follows some rules.
- All nodes in a parse tree must be terminal symbols.
- The intermediate nodes have to be nonterminal.
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To get the original input string, use in-order traversal.
Example
a+x*y is the expression we will use to represent the pare tree.
