Redescent

Redescent is a term used in the field of computer science, particularly in the context of programming languages and compilers. It refers to the process of descending through a parse tree or abstract syntax tree (AST) to perform various operations, such as code generation, optimization, or semantic analysis. This process is often contrasted with "ascent," which involves moving up the tree, typically during the parsing phase.

The term "redescent" is often used in the context of recursive descent parsers, which are a type of top-down parser that constructs the parse tree by recursively calling functions corresponding to different grammar rules. In a redescending approach, the parser would typically start at the root of the parse tree and move downwards, applying rules and generating code or performing other operations as it goes.

One of the key advantages of redescending is its simplicity and ease of implementation, especially for languages with a relatively straightforward grammar. However, it can also be less efficient than other parsing techniques, such as shift-reduce parsing, for more complex grammars.

In summary, redescending is a technique used in the construction and manipulation of parse trees, particularly in the context of recursive descent parsers. It involves descending through the tree to perform various operations, and is often contrasted with the ascent phase of parsing.