Narrowing conversion
A narrowing conversion converts a value to a type with a smaller representable range or lower precision, potentially losing information.
100 Java Mistakes and How to Avoid Them
A narrowing conversion converts a value to a type with a smaller representable range or less general numeric domain, potentially discarding information.
- How it is used
- Explains how Java casts and compound assignments can discard numeric information and cause incorrect program behavior.
- How deep it goes
- Works through overflow, bit loss, widening order, and analyzer limits, then stops short of a general numeric-conversion taxonomy.
- Examples
- Uses file lengths, character multiplication, negative bytes, and unsigned right shifts as concrete failure cases.
- What you can do after
- Diagnose unsafe casts and compound assignments, then replace them with range checks, exact conversion, or wider types.
Read how 100 Java Mistakes and How to Avoid Them explains narrowing conversion →
Modern C
A narrowing conversion is a conversion to a type whose representable range or precision cannot preserve all values of the source type.
- How it is used
- Warns against value loss in assignments and mixed-type arithmetic.
- How deep it goes
- Explains fitting values, overflow-related results, precision loss, and mixed signedness, but defers broader type-rule details.
- Examples
- Uses integer assignments, floating-point expressions, and signed-versus-unsigned comparisons to expose harmless and dangerous conversions.
- What you can do after
- Evaluate C conversions for representability, information loss, precision loss, and mixed signedness.
Modern C, Third Edition
A narrowing conversion is a conversion to a type that represents a smaller range or less precise set of values than the source type.
- How it is used
- Uses implicit conversions to evaluate whether assignments and mixed-type operations preserve values safely.
- How deep it goes
- Explains value-fit checks, literal-specific behavior, unsigned modular conversion, and precision loss in mixed arithmetic.
- Examples
- Uses signed and unsigned assignments, hexadecimal and decimal minimum values, and mixed integer-floating-point expressions.
- What you can do after
- Evaluate whether conversions preserve values and identify cases that may lose range, precision, or information.
Read how Modern C, Third Edition explains narrowing conversion →
Related concepts
- implicit conversionkind of · Implicit conversion is an automatic change of a value from one type to another according to language rules, without an explicit conversion operation in the source code.
- augmented assignmentused by · Augmented assignment is syntax that combines an operation with assignment to update a variable or object using its current value.
- uniform initializationcontrasts with · Uniform initialization is C++ syntax that uses braces to initialize objects and values.
- data conversionimplemented by · Data conversion is the transformation of a value or data from one type, format, or representation to another, explicitly or implicitly.
- numerical overflowproduces · Numerical overflow is the condition in which an arithmetic result falls outside the range representable by its numeric type or format.
- widening conversioncontrasts with · A widening conversion converts a value to a type with a broader representable range or compatible numeric domain without requiring an explicit cast or conversion operation.
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