Parsing, token, regular expressions

Middle PRO

Definitions

Parsing — turning input (text, bytes) into a structure that's convenient to work with: JSON → model, string → number, HTML → DOM.
A token in parsing is the smallest meaningful unit of input (a number, a name, a bracket); a lexer cuts text into tokens and a parser builds a structure from them. (Not to be confused with an auth token — the string the client sends in Authorization: Bearer ....)
A regular expression is a pattern for finding and extracting substrings: #(\d+) matches "#4521". In Swift 5.7+ that's the /.../ literal and RegexBuilder; in Foundation, NSRegularExpression.

In an iOS context "parsing" almost always means JSON via Codable.

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