Inline function
An inline function is a function defined or designated for incorporation at its use site, either syntactically or through compiler substitution, rather than necessarily invoked through an ordinary call.
Modern C
inline is a C function specifier that permits a function definition to be suitable for direct integration into callers without changing its semantics.
- How it is used
- Uses inline functions to expose small operations for optimization and to replace function-like macros when argument types are known.
- How deep it goes
- Explains call-site optimization and header layout, while making actual inlining a compiler choice rather than a guarantee.
- Examples
- Contrasts squaring a counter through a macro and an inline function, then shows a header definition with a separate declaration.
- What you can do after
- Build it from scratch: define a typed inline helper in a header and arrange its instantiation in one translation unit.
Modern C, Third Edition
inline is a C function specifier that permits a definition to suggest inline substitution of a function's body at call sites without requiring the compiler to perform that substitution.
- How it is used
- Uses inline for small functions that may benefit from call-site optimization and for typed replacements for function-like macros.
- How deep it goes
- Explains definition visibility, call overhead, optimization opportunities, and a header-plus-one-translation-unit arrangement without promising substitution.
- Examples
- Contrasts squaring a side-effecting call by macro and inline function, then illustrates a header definition and its companion declaration.
- What you can do after
- Apply inline to suitable small functions while preserving typed calls, arranging visible definitions, and measuring any claimed performance gain.
Kotlin in Action, 2E
An inline function is a Kotlin function whose body can be substituted at its call sites by the compiler and which can declare reified type parameters.
- How it is used
- Enables efficient higher-order helpers and collection operations while permitting non-local returns from their lambdas.
- How deep it goes
- Explains call-site bytecode substitution, lambda restrictions, performance tradeoffs, and reified runtime type checks.
- Examples
- Uses a locking helper, collection filter/map operations, and filterIsInstance on a mixed String and Int list.
- What you can do after
- Apply it via Kotlin inline and reified declarations to design small lambda-taking helpers and runtime type checks.
Grokking Simplicity
A function defined at the place in a program where it is used rather than assigned to a separate name.
- How it is used
- Uses short anonymous callbacks directly with higher-order functions such as map and withLogging.
- How deep it goes
- Defines inline, anonymous, global, and local functions, then demonstrates callbacks and refactoring limits.
- Examples
- Uses customer emails, greetings, logging, and purchase filtering and mapping to demonstrate inline callbacks.
- What you can do after
- Apply inline functions as map callbacks and recognize when naming a function improves reuse and clarity.
Related concepts
- functionkind of · A function is a callable program unit that performs an operation, may accept inputs, and can produce a result or side effect.
- function-like macrocontrasts with · A function-like macro is a macro invoked with function-like syntax that accepts token input and expands or transforms it into generated source.
- header fileconfigures · A header file is a source file containing declarations, definitions, macros, or other interface information intended for inclusion in one or more source files during compilation.
- filteringincludes · Filtering is the operation of selecting or excluding items from data or a collection according to specified criteria.
- non-local returnuses · A non-local return is a control-flow transfer that exits an enclosing function or computation from within nested code.
- lambdauses · A lambda is a language construct that defines an unnamed function or callable, often as a value.
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