Overload Resolution Back To Basics Ansel Sermersheim & Barbara Geller CppCon - October 2021 1Introduction ● Prologue ● Overload vs Override ● Why is Overload Resolution Required ● Definitions ● What What is Overload Resolution ● When will declaring an Overload fail ● Overview of the Process ● When to Use Overloads vs Using a Template ● Process to find the Best Overload ● When the Best Match is Not presentations for C++ user groups ■ United States, Germany, Netherlands, England 4Overload Resolution ● Overload vs Override ○ definition of polymorphism ■ having many forms ■ when there are two

UnicodeString; AIndex: Integer) : UCS4Char; Overload function ConvertToUtf32(const AString: UnicodeString; AIndex: Integer; out ACharLength: Integer) : UCS4Char; Overload function ConvertToUtf32(const AHighSurrogate: AHighSurrogate: UnicodeChar; const ALowSurrogate: UnicodeChar) : UCS4Char ; Overload Visibility: default Description: ConvertToUtf32 is a shortcut for TCharacter.ConvertToUtf32 (249). See also: TCharacter function GetNumericValue(AChar: UnicodeChar) : Double; Overload function GetNumericValue(const AString: UnicodeString; AIndex: Integer) : Double; Overload Visibility: default Description: GetNumericValue

Name Lookup Argument Dependent Lookup Two-Phase Lookup Template Argument Deduction SFINAE Overload Resolution (Viable) Candidate Functions Ranking Ambiguous Function Calls Access Labels Name Lookup Argument Dependent Lookup Two-Phase Lookup Template Argument Deduction SFINAE Overload Resolution (Viable) Candidate Functions Ranking Ambiguous Function Calls Access Labels the current scope. If none is found, proceed into the next surrounding scope. This results in an overload set.Overview 8 Template Argument Deduction Name Lookup Template Argument Deduction For

arguments in calls [call-arg] Check argument types [arg-type] Check calls to overloaded functions [call-overload] Check validity of types [valid-type] Require annotation if variable type is unclear [var-annotated] used where expected [literal-required] Check that overloaded functions have an implementation [no-overload- impl] Check that coroutine return value is used [unused-coroutine] Warn about top level await expressions Check for implicit bytes coercions [str-bytes-safe] Check that overloaded functions don’t overlap [overload-overlap] Notify about an annotation in an unchecked function [annotation- unchecked] Report syntax

arguments in calls [call-arg] Check argument types [arg-type] Check calls to overloaded functions [call-overload] Check validity of types [valid-type] Require annotation if variable type is unclear [var-annotated] used where expected [literal-required] Check that overloaded functions have an implementation [no-overload- impl] Check that coroutine return value is used [unused-coroutine] Warn about top level await expressions Check for implicit bytes coercions [str-bytes-safe] Check that overloaded functions don’t overlap [overload-overlap] Notify about an annotation in an unchecked function [annotation- unchecked] Report syntax

occasionally need to elide actual logic in regular Python code – for example, when writing methods in overload variants or custom protocols. The recommended style is to use ellipses to do so, just like in stub achieved by combining with @overload: from typing import Any, Callable, Optional, TypeVar, overload F = TypeVar('F', bound=Callable[..., Any]) # Bare decorator usage @overload def atomic(__func: F) -> -> F: ... # Decorator with arguments @overload def atomic(*, savepoint: bool = True) -> Callable[[F], F]: ... # Implementation def atomic(__func: Optional[Callable[..., Any]] = None, *, savepoint: bool

occasionally need to elide actual logic in regular Python code – for example, when writing methods in overload variants or custom protocols. The recommended style is to use ellipses to do so, just like in stub achieved by combining with @overload: from typing import Any, Callable, Optional, TypeVar, overload F = TypeVar('F', bound=Callable[..., Any]) # Bare decorator usage @overload def atomic(__func: F) -> -> F: ... # Decorator with arguments @overload def atomic(*, savepoint: bool = True) -> Callable[[F], F]: ... # Implementation def atomic(__func: Optional[Callable[..., Any]] = None, *, savepoint: bool

get(tuple) has to iterate over the first N types. Advanced approach There is a way to exploit overload resolution to have O (log (N)) compile-time access. Indexing 1 // Index constant type 2 template template 23 tuple(const T&...) −> tuple ; Result mytuple[index<3>] leverages overload resolution to access the element at compile-time. CppCon - Vincent Reverdy - September 17th, 2020 Conclusion Runtime element access of a static sequence: variadic implementation Expressivity goal overload_sequence(F...)[i](Args...) should return the result of the i-th function F on the arguments Args

&anl, &serial}; for (auto o: outputs) { std::visit(out_overload, o ); } std::visit determine type of o and calls the function out_overload(cast(o) ) Answers what to use for type std::visit 20 The Overload Idiom A Polymorphic Invokable With Lambdas All The Way DownCppcon 2023 | Rud Merriam | A Journey into Non-Virtual Polymorphism 21 template struct Overload : Ls . Argument Deduction) // needed prior to C++ 20 template Overload(Ls...) -> Overload; auto out_overload = Overload { digi_out, [](AnalogPin* pin) { pin->write(); }, [](SerialPort*

Introduction  This session will examine each of these features in turn:  Function overloading and overload resolution  Name lookup  Default function arguments  Function templates  For each feature, put(char const *s, FILE *f); 11 Overload Resolution  When the compiler encounters a call to an overloaded function, it selects the function to call using overload resolution.  The compiler matches: const *s); 12Back to Basics - Function Call Resolution Copyright © 2024 by Ben Saks and Dan Saks Overload Resolution  If the compiler can’t find a function that accepts the specified arguments, it issues