Magic number
A magic number is an unexplained numeric literal embedded directly in code rather than represented by a descriptive name or explanation.
Learn Haskell by Example
A magic number is a distinctive value in a file header that identifies the file format and sometimes its encoding variant.
- How it is used
- Uses header signatures to select PNM parsing and validate image data, then to categorize files before later processing.
- How deep it goes
- Builds parsers from fixed-string matching through remainder-carrying composition and branches header parsing on previously read markers.
- Examples
- Demonstrates PBM and PGM headers, P1–P6 parser cases, and byte signatures for BMP, PNG, JPEG, bzip2, and gzip.
- What you can do after
- Apply it via Data.ByteString and Haskell parsers to recognize supported file formats and reject inconsistent PNM data.
Learn AI-Assisted Python Programming, Second Edition
A magic number is an unexplained numeric literal embedded directly in code instead of being represented by a named parameter or variable.
- How it is used
- Keeps game behavior configurable by moving changeable numeric settings into parameters.
- How deep it goes
- Defines magic numbers and gives a review heuristic, but does not develop broader refactoring techniques.
- Examples
- Uses secret-code length and maximum guesses in a configurable guessing game.
- What you can do after
- Apply it by replacing changeable raw numbers with named parameters or variables.
Read how Learn AI-Assisted Python Programming, Second Edition explains magic number →
Related concepts
- enumalternative to · An enum is a type or language construct whose values are selected from a finite set of named alternatives, which may carry associated data.
- calc()addressed by · The CSS calc() function evaluates an arithmetic expression involving compatible CSS values and units to produce a computed value.
- inputaddressed by · An input is a value, information, or signal supplied to a system, computation, or interface for processing or to influence its behavior.
- maintainabilitycontrasts with · Maintainability is the degree to which software can be understood, modified, corrected, tested, repaired, or kept operational with reasonable effort over time.
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