-
Notifications
You must be signed in to change notification settings - Fork 13
Expand file tree
/
Copy pathfunction-overloading.html
More file actions
195 lines (165 loc) · 46.5 KB
/
function-overloading.html
File metadata and controls
195 lines (165 loc) · 46.5 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
<!DOCTYPE html>
<html lang="en-US">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width,initial-scale=1">
<title>C++ | Function Overloading</title>
<meta name="generator" content="VuePress 1.8.2">
<link rel="icon" type="image/png" sizes="32x32" href="/favicon-32x32.png">
<link rel="icon" type="image/png" sizes="16x16" href="/favicon-16x16.png">
<link rel="manifest" href="/site.webmanifest">
<link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon.png">
<link rel="mask-icon" href="/safari-pinned-tab.svg" color="#5bbad5">
<meta name="description" content="What is Function Overloading?, Return Type in Function Overloading, Member Function cv-qualifier Overloading">
<meta property="og:site_name" content="DevTut">
<meta property="og:title" content="C++ | Function Overloading">
<meta property="og:description" content="What is Function Overloading?, Return Type in Function Overloading, Member Function cv-qualifier Overloading">
<meta property="og:type" content="article">
<meta property="og:url" content="/cpp/function-overloading.html">
<meta property="og:image" content="/logo.png">
<meta name="twitter:title" content="C++ | Function Overloading">
<meta name="twitter:description" content="What is Function Overloading?, Return Type in Function Overloading, Member Function cv-qualifier Overloading">
<meta name="twitter:url" content="/cpp/function-overloading.html">
<meta name="twitter:card" content="summary_large_image">
<meta name="twitter:image" content="/logo.png">
<meta name="theme-color" content="#ffffff">
<meta name="apple-mobile-web-app-capable" content="yes">
<meta name="apple-mobile-web-app-status-bar-style" content="black">
<meta name="msapplication-TileImage" content="/mstile-150x150.png">
<meta name="msapplication-TileColor" content="#da532c">
<meta name="google-site-verification" content="76_rKXgwMVIjd-axJC_1zPV9OS4mEjvtgjYOWVkAdnQ">
<link rel="preload" href="/assets/css/0.styles.60619e34.css" as="style"><link rel="preload" href="/assets/js/app.1779e102.js" as="script"><link rel="preload" href="/assets/js/3.2cfa8016.js" as="script"><link rel="preload" href="/assets/js/657.2f669db8.js" as="script">
<link rel="stylesheet" href="/assets/css/0.styles.60619e34.css">
</head>
<body>
<div id="app" data-server-rendered="true"><div class="theme-container"><header class="navbar"><div class="sidebar-button"><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" role="img" viewBox="0 0 448 512" class="icon"><path fill="currentColor" d="M436 124H12c-6.627 0-12-5.373-12-12V80c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12z"></path></svg></div> <a href="/" class="home-link router-link-active"><!----> <span class="site-name">DevTut</span></a> <div class="links"><form id="search-form" role="search" class="algolia-search-wrapper search-box"><input id="algolia-search-input" class="search-query"></form> <nav class="nav-links can-hide"> <a href="https://github.com/devtut/generate" target="_blank" rel="noopener noreferrer" class="repo-link">
GitHub
<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav></div></header> <div class="sidebar-mask"></div> <aside class="sidebar"><nav class="nav-links"> <a href="https://github.com/devtut/generate" target="_blank" rel="noopener noreferrer" class="repo-link">
GitHub
<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav> <ul class="sidebar-links"><li><section class="sidebar-group depth-0"><p class="sidebar-heading open"><span>C++</span> <!----></p> <ul class="sidebar-links sidebar-group-items"><li><a href="/cpp/" aria-current="page" class="sidebar-link">Disclaimer</a></li><li><a href="/cpp/getting-started-with-cpp.html" class="sidebar-link">Getting started with C++</a></li><li><a href="/cpp/literals.html" class="sidebar-link">Literals</a></li><li><a href="/cpp/operator-precedence.html" class="sidebar-link">operator precedence</a></li><li><a href="/cpp/floating-point-arithmetic.html" class="sidebar-link">Floating Point Arithmetic</a></li><li><a href="/cpp/bit-operators.html" class="sidebar-link">Bit Operators</a></li><li><a href="/cpp/bit-manipulation.html" class="sidebar-link">Bit Manipulation</a></li><li><a href="/cpp/bit-fields.html" class="sidebar-link">Bit fields</a></li><li><a href="/cpp/arrays.html" class="sidebar-link">Arrays</a></li><li><a href="/cpp/iterators.html" class="sidebar-link">Iterators</a></li><li><a href="/cpp/basic-input-output-in-c.html" class="sidebar-link">Basic input/output in c++</a></li><li><a href="/cpp/loops.html" class="sidebar-link">Loops</a></li><li><a href="/cpp/file-i-o.html" class="sidebar-link">File I/O</a></li><li><a href="/cpp/cpp-streams.html" class="sidebar-link">C++ Streams</a></li><li><a href="/cpp/stream-manipulators.html" class="sidebar-link">Stream manipulators</a></li><li><a href="/cpp/flow-control.html" class="sidebar-link">Flow Control</a></li><li><a href="/cpp/metaprogramming.html" class="sidebar-link">Metaprogramming</a></li><li><a href="/cpp/const-keyword.html" class="sidebar-link">const keyword</a></li><li><a href="/cpp/mutable-keyword.html" class="sidebar-link">mutable keyword</a></li><li><a href="/cpp/friend-keyword.html" class="sidebar-link">Friend keyword</a></li><li><a href="/cpp/type-keywords.html" class="sidebar-link">Type Keywords</a></li><li><a href="/cpp/basic-type-keywords.html" class="sidebar-link">Basic Type Keywords</a></li><li><a href="/cpp/variable-declaration-keywords.html" class="sidebar-link">Variable Declaration Keywords</a></li><li><a href="/cpp/keywords.html" class="sidebar-link">Keywords</a></li><li><a href="/cpp/returning-several-values-from-a-function.html" class="sidebar-link">Returning several values from a function</a></li><li><a href="/cpp/polymorphism.html" class="sidebar-link">Polymorphism</a></li><li><a href="/cpp/references.html" class="sidebar-link">References</a></li><li><a href="/cpp/value-and-reference-semantics.html" class="sidebar-link">Value and Reference Semantics</a></li><li><a href="/cpp/c-function-call-by-value-vs-call-by-reference.html" class="sidebar-link">C++ function "call by value" vs. "call by reference"</a></li><li><a href="/cpp/copying-vs-assignment.html" class="sidebar-link">Copying vs Assignment</a></li><li><a href="/cpp/pointers.html" class="sidebar-link">Pointers</a></li><li><a href="/cpp/pointers-to-members.html" class="sidebar-link">Pointers to members</a></li><li><a href="/cpp/the-this-pointer.html" class="sidebar-link">The This Pointer</a></li><li><a href="/cpp/smart-pointers.html" class="sidebar-link">Smart Pointers</a></li><li><a href="/cpp/classes-structures.html" class="sidebar-link">Classes/Structures</a></li><li><a href="/cpp/function-overloading.html" aria-current="page" class="active sidebar-link">Function Overloading</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header"><a href="/cpp/function-overloading.html#what-is-function-overloading" class="sidebar-link">What is Function Overloading?</a></li><li class="sidebar-sub-header"><a href="/cpp/function-overloading.html#return-type-in-function-overloading" class="sidebar-link">Return Type in Function Overloading</a></li><li class="sidebar-sub-header"><a href="/cpp/function-overloading.html#member-function-cv-qualifier-overloading" class="sidebar-link">Member Function cv-qualifier Overloading</a></li></ul></li><li><a href="/cpp/operator-overloading.html" class="sidebar-link">Operator Overloading</a></li><li><a href="/cpp/function-template-overloading.html" class="sidebar-link">Function Template Overloading</a></li><li><a href="/cpp/virtual-member-functions.html" class="sidebar-link">Virtual Member Functions</a></li><li><a href="/cpp/inline-functions.html" class="sidebar-link">Inline functions</a></li><li><a href="/cpp/special-member-functions.html" class="sidebar-link">Special Member Functions</a></li><li><a href="/cpp/non-static-member-functions.html" class="sidebar-link">Non-Static Member Functions</a></li><li><a href="/cpp/constant-class-member-functions.html" class="sidebar-link">Constant class member functions</a></li><li><a href="/cpp/c-containers.html" class="sidebar-link">C++ Containers</a></li><li><a href="/cpp/namespaces.html" class="sidebar-link">Namespaces</a></li><li><a href="/cpp/header-files.html" class="sidebar-link">Header Files</a></li><li><a href="/cpp/using-declaration.html" class="sidebar-link">Using declaration</a></li><li><a href="/cpp/std-string.html" class="sidebar-link">std::string</a></li><li><a href="/cpp/std-array.html" class="sidebar-link">std::array</a></li><li><a href="/cpp/std-vector.html" class="sidebar-link">std::vector</a></li><li><a href="/cpp/std-map.html" class="sidebar-link">std::map</a></li><li><a href="/cpp/std-optional.html" class="sidebar-link">std::optional</a></li><li><a href="/cpp/std-function-to-wrap-any-element-that-is-callable.html" class="sidebar-link">std::function: To wrap any element that is callable</a></li><li><a href="/cpp/std-forward-list.html" class="sidebar-link">std::forward_list</a></li><li><a href="/cpp/std-pair.html" class="sidebar-link">std::pair</a></li><li><a href="/cpp/std-atomics.html" class="sidebar-link">std::atomics</a></li><li><a href="/cpp/std-variant.html" class="sidebar-link">std::variant</a></li><li><a href="/cpp/std-iomanip.html" class="sidebar-link">std::iomanip</a></li><li><a href="/cpp/std-any.html" class="sidebar-link">std::any</a></li><li><a href="/cpp/std-set-and-std-multiset.html" class="sidebar-link">std::set and std::multiset</a></li><li><a href="/cpp/std-integer-sequence.html" class="sidebar-link">std::integer_sequence</a></li><li><a href="/cpp/using-std-unordered-map.html" class="sidebar-link">Using std::unordered_map</a></li><li><a href="/cpp/standard-library-algorithms.html" class="sidebar-link">Standard Library Algorithms</a></li><li><a href="/cpp/the-iso-c-standard.html" class="sidebar-link">The ISO C++ Standard</a></li><li><a href="/cpp/inline-variables.html" class="sidebar-link">Inline variables</a></li><li><a href="/cpp/random-number-generation.html" class="sidebar-link">Random number generation</a></li><li><a href="/cpp/date-and-time-using-chrono-header.html" class="sidebar-link">Date and time using header</a></li><li><a href="/cpp/sorting.html" class="sidebar-link">Sorting</a></li><li><a href="/cpp/enumeration.html" class="sidebar-link">Enumeration</a></li><li><a href="/cpp/iteration.html" class="sidebar-link">Iteration</a></li><li><a href="/cpp/regular-expressions.html" class="sidebar-link">Regular expressions</a></li><li><a href="/cpp/implementation-defined-behavior.html" class="sidebar-link">Implementation-defined behavior</a></li><li><a href="/cpp/exceptions.html" class="sidebar-link">Exceptions</a></li><li><a href="/cpp/lambdas.html" class="sidebar-link">Lambdas</a></li><li><a href="/cpp/value-categories.html" class="sidebar-link">Value Categories</a></li><li><a href="/cpp/preprocessor.html" class="sidebar-link">Preprocessor</a></li><li><a href="/cpp/data-structures-in-c.html" class="sidebar-link">Data Structures in C++</a></li><li><a href="/cpp/templates.html" class="sidebar-link">Templates</a></li><li><a href="/cpp/expression-templates.html" class="sidebar-link">Expression templates</a></li><li><a href="/cpp/curiously-recurring-template-pattern-crtp.html" class="sidebar-link">Curiously Recurring Template Pattern (CRTP)</a></li><li><a href="/cpp/threading.html" class="sidebar-link">Threading</a></li><li><a href="/cpp/thread-synchronization-structures.html" class="sidebar-link">Thread synchronization structures</a></li><li><a href="/cpp/the-rule-of-three-five-and-zero.html" class="sidebar-link">The Rule of Three, Five, And Zero</a></li><li><a href="/cpp/raii-resource-acquisition-is-initialization.html" class="sidebar-link">RAII: Resource Acquisition Is Initialization</a></li><li><a href="/cpp/rtti-run-time-type-information.html" class="sidebar-link">RTTI: Run-Time Type Information</a></li><li><a href="/cpp/mutexes.html" class="sidebar-link">Mutexes</a></li><li><a href="/cpp/recursive-mutex.html" class="sidebar-link">Recursive Mutex</a></li><li><a href="/cpp/semaphore.html" class="sidebar-link">Semaphore</a></li><li><a href="/cpp/futures-and-promises.html" class="sidebar-link">Futures and Promises</a></li><li><a href="/cpp/atomic-types.html" class="sidebar-link">Atomic Types</a></li><li><a href="/cpp/type-erasure.html" class="sidebar-link">Type Erasure</a></li><li><a href="/cpp/explicit-type-conversions.html" class="sidebar-link">Explicit type conversions</a></li><li><a href="/cpp/unnamed-types.html" class="sidebar-link">Unnamed types</a></li><li><a href="/cpp/type-traits.html" class="sidebar-link">Type Traits</a></li><li><a href="/cpp/return-type-covariance.html" class="sidebar-link">Return Type Covariance</a></li><li><a href="/cpp/layout-of-object-types.html" class="sidebar-link">Layout of object types</a></li><li><a href="/cpp/type-inference.html" class="sidebar-link">Type Inference</a></li><li><a href="/cpp/typedef-and-type-aliases.html" class="sidebar-link">Typedef and type aliases</a></li><li><a href="/cpp/type-deduction.html" class="sidebar-link">type deduction</a></li><li><a href="/cpp/trailing-return-type.html" class="sidebar-link">Trailing return type</a></li><li><a href="/cpp/alignment.html" class="sidebar-link">Alignment</a></li><li><a href="/cpp/perfect-forwarding.html" class="sidebar-link">Perfect Forwarding</a></li><li><a href="/cpp/decltype.html" class="sidebar-link">decltype</a></li><li><a href="/cpp/sfinae-substitution-failure-is-not-an-error.html" class="sidebar-link">SFINAE (Substitution Failure Is Not An Error)</a></li><li><a href="/cpp/undefined-behavior.html" class="sidebar-link">Undefined Behavior</a></li><li><a href="/cpp/overload-resolution.html" class="sidebar-link">Overload resolution</a></li><li><a href="/cpp/move-semantics.html" class="sidebar-link">Move Semantics</a></li><li><a href="/cpp/pimpl-idiom.html" class="sidebar-link">Pimpl Idiom</a></li><li><a href="/cpp/auto.html" class="sidebar-link">auto</a></li><li><a href="/cpp/copy-elision.html" class="sidebar-link">Copy Elision</a></li><li><a href="/cpp/fold-expressions.html" class="sidebar-link">Fold Expressions</a></li><li><a href="/cpp/unions.html" class="sidebar-link">Unions</a></li><li><a href="/cpp/design-pattern-implementation-in-c.html" class="sidebar-link">Design pattern implementation in C++</a></li><li><a href="/cpp/singleton-design-pattern.html" class="sidebar-link">Singleton Design Pattern</a></li><li><a href="/cpp/user-defined-literals.html" class="sidebar-link">User-Defined Literals</a></li><li><a href="/cpp/memory-management.html" class="sidebar-link">Memory management</a></li><li><a href="/cpp/c-11-memory-model.html" class="sidebar-link">C++11 Memory Model</a></li><li><a href="/cpp/scopes.html" class="sidebar-link">Scopes</a></li><li><a href="/cpp/static-assert.html" class="sidebar-link">static_assert</a></li><li><a href="/cpp/constexpr.html" class="sidebar-link">constexpr</a></li><li><a href="/cpp/one-definition-rule-odr.html" class="sidebar-link">One Definition Rule (ODR)</a></li><li><a href="/cpp/unspecified-behavior.html" class="sidebar-link">Unspecified behavior</a></li><li><a href="/cpp/argument-dependent-name-lookup.html" class="sidebar-link">Argument Dependent Name Lookup</a></li><li><a href="/cpp/attributes.html" class="sidebar-link">Attributes</a></li><li><a href="/cpp/recursion-in-c.html" class="sidebar-link">Recursion in C++</a></li><li><a href="/cpp/arithmitic-metaprogramming.html" class="sidebar-link">Arithmitic Metaprogramming</a></li><li><a href="/cpp/callable-objects.html" class="sidebar-link">Callable Objects</a></li><li><a href="/cpp/client-server-examples.html" class="sidebar-link">Client server examples</a></li><li><a href="/cpp/const-correctness.html" class="sidebar-link">Const Correctness</a></li><li><a href="/cpp/parameter-packs.html" class="sidebar-link">Parameter packs</a></li><li><a href="/cpp/build-systems.html" class="sidebar-link">Build Systems</a></li><li><a href="/cpp/concurrency-with-openmp.html" class="sidebar-link">Concurrency With OpenMP</a></li><li><a href="/cpp/resource-management.html" class="sidebar-link">Resource Management</a></li><li><a href="/cpp/storage-class-specifiers.html" class="sidebar-link">Storage class specifiers</a></li><li><a href="/cpp/linkage-specifications.html" class="sidebar-link">Linkage specifications</a></li><li><a href="/cpp/digit-separators.html" class="sidebar-link">Digit separators</a></li><li><a href="/cpp/c-incompatibilities.html" class="sidebar-link">C incompatibilities</a></li><li><a href="/cpp/side-by-side-comparisons-of-classic-c-examples-solved-via-c-vs-c-11-vs-c-14-vs-c-17.html" class="sidebar-link">Side by Side Comparisons of classic C++ examples solved via C++ vs C++11 vs C++14 vs C++17</a></li><li><a href="/cpp/compiling-and-building.html" class="sidebar-link">Compiling and Building</a></li><li><a href="/cpp/common-compile-linker-errors-gcc.html" class="sidebar-link">Common compile/linker errors (GCC)</a></li><li><a href="/cpp/more-undefined-behaviors-in-c.html" class="sidebar-link">More undefined behaviors in C++</a></li><li><a href="/cpp/unit-testing-in-c.html" class="sidebar-link">Unit Testing in C++</a></li><li><a href="/cpp/c-debugging-and-debug-prevention-tools-techniques.html" class="sidebar-link">C++ Debugging and Debug-prevention Tools & Techniques</a></li><li><a href="/cpp/optimization-in-c.html" class="sidebar-link">Optimization in C++</a></li><li><a href="/cpp/optimization.html" class="sidebar-link">Optimization</a></li><li><a href="/cpp/profiling.html" class="sidebar-link">Profiling</a></li><li><a href="/cpp/refactoring-techniques.html" class="sidebar-link">Refactoring Techniques</a></li><li><a href="/cpp/internationalization-in-c.html" class="sidebar-link">Internationalization in C++</a></li><li><a href="/cpp/contributors.html" class="sidebar-link">The Contributors</a></li></ul></section></li></ul> </aside> <main class="page"> <div class="theme-default-content content__default"><h1 id="function-overloading"><a href="#function-overloading" class="header-anchor">#</a> Function Overloading</h1> <p>See also separate topic on <a href="http://stackoverflow.com/documentation/c%2B%2B/2021/overload-resolution#t=201705051758072433148" target="_blank" rel="noopener noreferrer">Overload Resolution<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></p> <h2 id="what-is-function-overloading"><a href="#what-is-function-overloading" class="header-anchor">#</a> What is Function Overloading?</h2> <p>Function overloading is having multiple functions declared in the same scope with the exact same name exist in the same place (known as <strong>scope</strong>) differing only in their <strong>signature</strong>, meaning the arguments they accept.</p> <p>Suppose you are writing a series of functions for generalized printing capabilities, beginning with <code>std::string</code>:</p> <div class="language-cpp extra-class"><pre class="language-cpp"><code><span class="token keyword">void</span> <span class="token function">print</span><span class="token punctuation">(</span><span class="token keyword">const</span> std<span class="token double-colon punctuation">::</span>string <span class="token operator">&</span>str<span class="token punctuation">)</span>
<span class="token punctuation">{</span>
std<span class="token double-colon punctuation">::</span>cout <span class="token operator"><<</span> <span class="token string">"This is a string: "</span> <span class="token operator"><<</span> str <span class="token operator"><<</span> std<span class="token double-colon punctuation">::</span>endl<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre></div><p>This works fine, but suppose you want a function that also accepts an <code>int</code> and prints that too. You could write:</p> <div class="language-cpp extra-class"><pre class="language-cpp"><code><span class="token keyword">void</span> <span class="token function">print_int</span><span class="token punctuation">(</span><span class="token keyword">int</span> num<span class="token punctuation">)</span>
<span class="token punctuation">{</span>
std<span class="token double-colon punctuation">::</span>cout <span class="token operator"><<</span> <span class="token string">"This is an int: "</span> <span class="token operator"><<</span> num <span class="token operator"><<</span> std<span class="token double-colon punctuation">::</span>endl<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre></div><p>But because the two functions accept different parameters, you can simply write:</p> <div class="language-cpp extra-class"><pre class="language-cpp"><code><span class="token keyword">void</span> <span class="token function">print</span><span class="token punctuation">(</span><span class="token keyword">int</span> num<span class="token punctuation">)</span>
<span class="token punctuation">{</span>
std<span class="token double-colon punctuation">::</span>cout <span class="token operator"><<</span> <span class="token string">"This is an int: "</span> <span class="token operator"><<</span> num <span class="token operator"><<</span> std<span class="token double-colon punctuation">::</span>endl<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre></div><p>Now you have 2 functions, both named <code>print</code>, but with different signatures. One accepts <code>std::string</code>, the other one an <code>int</code>. Now you can call them without worrying about different names:</p> <div class="language-cpp extra-class"><pre class="language-cpp"><code><span class="token function">print</span><span class="token punctuation">(</span><span class="token string">"Hello world!"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//prints "This is a string: Hello world!"</span>
<span class="token function">print</span><span class="token punctuation">(</span><span class="token number">1337</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//prints "This is an int: 1337"</span>
</code></pre></div><p>Instead of:</p> <div class="language-cpp extra-class"><pre class="language-cpp"><code><span class="token function">print</span><span class="token punctuation">(</span><span class="token string">"Hello world!"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">print_int</span><span class="token punctuation">(</span><span class="token number">1337</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre></div><p>When you have overloaded functions, the compiler infers which of the functions to call from the parameters you provide it. Care must be taken when writing function overloads. For example, with implicit type conversions:</p> <div class="language-cpp extra-class"><pre class="language-cpp"><code><span class="token keyword">void</span> <span class="token function">print</span><span class="token punctuation">(</span><span class="token keyword">int</span> num<span class="token punctuation">)</span>
<span class="token punctuation">{</span>
std<span class="token double-colon punctuation">::</span>cout <span class="token operator"><<</span> <span class="token string">"This is an int: "</span> <span class="token operator"><<</span> num <span class="token operator"><<</span> std<span class="token double-colon punctuation">::</span>endl<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">void</span> <span class="token function">print</span><span class="token punctuation">(</span><span class="token keyword">double</span> num<span class="token punctuation">)</span>
<span class="token punctuation">{</span>
std<span class="token double-colon punctuation">::</span>cout <span class="token operator"><<</span> <span class="token string">"This is a double: "</span> <span class="token operator"><<</span> num <span class="token operator"><<</span> std<span class="token double-colon punctuation">::</span>endl<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre></div><p>Now it's not immediately clear which overload of <code>print</code> is called when you write:</p> <div class="language-cpp extra-class"><pre class="language-cpp"><code><span class="token function">print</span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre></div><p>And you might need to give your compiler some clues, like:</p> <div class="language-cpp extra-class"><pre class="language-cpp"><code><span class="token function">print</span><span class="token punctuation">(</span><span class="token generic-function"><span class="token function">static_cast</span><span class="token generic class-name"><span class="token operator"><</span><span class="token keyword">double</span><span class="token operator">></span></span></span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">print</span><span class="token punctuation">(</span><span class="token generic-function"><span class="token function">static_cast</span><span class="token generic class-name"><span class="token operator"><</span><span class="token keyword">int</span><span class="token operator">></span></span></span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">print</span><span class="token punctuation">(</span><span class="token number">5.0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre></div><p>Some care also needs to be taken when writing overloads that accept optional parameters:</p> <div class="language-cpp extra-class"><pre class="language-cpp"><code><span class="token comment">// WRONG CODE</span>
<span class="token keyword">void</span> <span class="token function">print</span><span class="token punctuation">(</span><span class="token keyword">int</span> num1<span class="token punctuation">,</span> <span class="token keyword">int</span> num2 <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token comment">//num2 defaults to 0 if not included</span>
<span class="token punctuation">{</span>
std<span class="token double-colon punctuation">::</span>cout <span class="token operator"><<</span> <span class="token string">"These are ints: << num1 << "</span> <span class="token operator">and</span> " <span class="token operator"><<</span> num2 <span class="token operator"><<</span> std<span class="token double-colon punctuation">::</span>endl<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">void</span> <span class="token function">print</span><span class="token punctuation">(</span><span class="token keyword">int</span> num<span class="token punctuation">)</span>
<span class="token punctuation">{</span>
std<span class="token double-colon punctuation">::</span>cout <span class="token operator"><<</span> <span class="token string">"This is an int: "</span> <span class="token operator"><<</span> num <span class="token operator"><<</span> std<span class="token double-colon punctuation">::</span>endl<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre></div><p>Because there's no way for the compiler to tell if a call like <code>print(17)</code> is meant for the first or second function because of the optional second parameter, this will fail to compile.</p> <h2 id="return-type-in-function-overloading"><a href="#return-type-in-function-overloading" class="header-anchor">#</a> Return Type in Function Overloading</h2> <p>Note that you cannot overload a function based on its return type. For example:</p> <div class="language-cpp extra-class"><pre class="language-cpp"><code><span class="token comment">// WRONG CODE</span>
std<span class="token double-colon punctuation">::</span>string <span class="token function">getValue</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token string">"hello"</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">int</span> <span class="token function">getValue</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">int</span> x <span class="token operator">=</span> <span class="token function">getValue</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre></div><p>This will cause a compilation error as the compiler will not be able to work out which version of <code>getValue</code> to call, even though the return type is assigned to an <code>int</code>.</p> <h2 id="member-function-cv-qualifier-overloading"><a href="#member-function-cv-qualifier-overloading" class="header-anchor">#</a> Member Function cv-qualifier Overloading</h2> <p>Functions within a class can be overloaded for when they are accessed through a cv-qualified reference to that class; this is most commonly used to overload for <code>const</code>, but can be used to overload for <code>volatile</code> and <code>const volatile</code>, too. This is because all non-static member functions take <code>this</code> as a hidden parameter, which the cv-qualifiers are applied to. This is most commonly used to overload for <code>const</code>, but can also be used for <code>volatile</code> and <code>const volatile</code>.</p> <p>This is necessary because a member function can only be called if it is at least as cv-qualified as the instance it's called on. While a non-<code>const</code> instance can call both <code>const</code> and non-<code>const</code> members, a <code>const</code> instance can only call <code>const</code> members. This allows a function to have different behaviour depending on the calling instance's cv-qualifiers, and allows the programmer to disallow functions for an undesired cv-qualifier(s) by not providing a version with that qualifier(s).</p> <p>A class with some basic <code>print</code> method could be <code>const</code> overloaded like so:</p> <div class="language-cpp extra-class"><pre class="language-cpp"><code><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><iostream></span></span>
<span class="token keyword">class</span> <span class="token class-name">Integer</span>
<span class="token punctuation">{</span>
<span class="token keyword">public</span><span class="token operator">:</span>
<span class="token function">Integer</span><span class="token punctuation">(</span><span class="token keyword">int</span> i_<span class="token punctuation">)</span><span class="token operator">:</span> i<span class="token punctuation">{</span>i_<span class="token punctuation">}</span><span class="token punctuation">{</span><span class="token punctuation">}</span>
<span class="token keyword">void</span> <span class="token function">print</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
std<span class="token double-colon punctuation">::</span>cout <span class="token operator"><<</span> <span class="token string">"int: "</span> <span class="token operator"><<</span> i <span class="token operator"><<</span> std<span class="token double-colon punctuation">::</span>endl<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">void</span> <span class="token function">print</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">const</span>
<span class="token punctuation">{</span>
std<span class="token double-colon punctuation">::</span>cout <span class="token operator"><<</span> <span class="token string">"const int: "</span> <span class="token operator"><<</span> i <span class="token operator"><<</span> std<span class="token double-colon punctuation">::</span>endl<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">protected</span><span class="token operator">:</span>
<span class="token keyword">int</span> i<span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
Integer i<span class="token punctuation">{</span><span class="token number">5</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token keyword">const</span> Integer <span class="token operator">&</span>ic <span class="token operator">=</span> i<span class="token punctuation">;</span>
i<span class="token punctuation">.</span><span class="token function">print</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// prints "int: 5"</span>
ic<span class="token punctuation">.</span><span class="token function">print</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// prints "const int: 5"</span>
<span class="token punctuation">}</span>
</code></pre></div><p>This is a key tenet of <code>const</code> correctness: By marking member functions as <code>const</code>, they are allowed to be called on <code>const</code> instances, which in turn allows functions to take instances as <code>const</code> pointers/references if they don't need to modify them. This allows code to specify whether it modifies state by taking unmodified parameters as <code>const</code> and modified parameters without cv-qualifiers, making code both safer and more readable.</p> <div class="language-cpp extra-class"><pre class="language-cpp"><code><span class="token keyword">class</span> <span class="token class-name">ConstCorrect</span>
<span class="token punctuation">{</span>
<span class="token keyword">public</span><span class="token operator">:</span>
<span class="token keyword">void</span> <span class="token function">good_func</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">const</span>
<span class="token punctuation">{</span>
std<span class="token double-colon punctuation">::</span>cout <span class="token operator"><<</span> <span class="token string">"I care not whether the instance is const."</span> <span class="token operator"><<</span> std<span class="token double-colon punctuation">::</span>endl<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">void</span> <span class="token function">bad_func</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
std<span class="token double-colon punctuation">::</span>cout <span class="token operator"><<</span> <span class="token string">"I can only be called on non-const, non-volatile instances."</span> <span class="token operator"><<</span> std<span class="token double-colon punctuation">::</span>endl<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token keyword">void</span> <span class="token function">i_change_no_state</span><span class="token punctuation">(</span><span class="token keyword">const</span> ConstCorrect<span class="token operator">&</span> cc<span class="token punctuation">)</span>
<span class="token punctuation">{</span>
std<span class="token double-colon punctuation">::</span>cout <span class="token operator"><<</span> <span class="token string">"I can take either a const or a non-const ConstCorrect."</span> <span class="token operator"><<</span> std<span class="token double-colon punctuation">::</span>endl<span class="token punctuation">;</span>
cc<span class="token punctuation">.</span><span class="token function">good_func</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// Good. Can be called from const or non-const instance.</span>
cc<span class="token punctuation">.</span><span class="token function">bad_func</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// Error. Can only be called from non-const instance.</span>
<span class="token punctuation">}</span>
<span class="token keyword">void</span> <span class="token function">const_incorrect_func</span><span class="token punctuation">(</span>ConstCorrect<span class="token operator">&</span> cc<span class="token punctuation">)</span>
<span class="token punctuation">{</span>
cc<span class="token punctuation">.</span><span class="token function">good_func</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// Good. Can be called from const or non-const instance.</span>
cc<span class="token punctuation">.</span><span class="token function">bad_func</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// Good. Can only be called from non-const instance.</span>
<span class="token punctuation">}</span>
</code></pre></div><p>A common usage of this is declaring accessors as <code>const</code>, and mutators as non-<code>const</code>.</p> <p>No class members can be modified within a <code>const</code> member function. If there is some member that you really need to modify, such as locking a <code>std::mutex</code>, you can declare it as <a href="http://stackoverflow.com/documentation/c%2B%2B/2705/mutable-keyword#t=201608042103196324218" target="_blank" rel="noopener noreferrer"><code>mutable</code><span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a>:</p> <div class="language-cpp extra-class"><pre class="language-cpp"><code><span class="token keyword">class</span> <span class="token class-name">Integer</span>
<span class="token punctuation">{</span>
<span class="token keyword">public</span><span class="token operator">:</span>
<span class="token function">Integer</span><span class="token punctuation">(</span><span class="token keyword">int</span> i_<span class="token punctuation">)</span><span class="token operator">:</span> i<span class="token punctuation">{</span>i_<span class="token punctuation">}</span><span class="token punctuation">{</span><span class="token punctuation">}</span>
<span class="token keyword">int</span> <span class="token function">get</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">const</span>
<span class="token punctuation">{</span>
std<span class="token double-colon punctuation">::</span>lock_guard<span class="token operator"><</span>std<span class="token double-colon punctuation">::</span>mutex<span class="token operator">></span> lock<span class="token punctuation">{</span>mut<span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token keyword">return</span> i<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">void</span> <span class="token function">set</span><span class="token punctuation">(</span><span class="token keyword">int</span> i_<span class="token punctuation">)</span>
<span class="token punctuation">{</span>
std<span class="token double-colon punctuation">::</span>lock_guard<span class="token operator"><</span>std<span class="token double-colon punctuation">::</span>mutex<span class="token operator">></span> lock<span class="token punctuation">{</span>mut<span class="token punctuation">}</span><span class="token punctuation">;</span>
i <span class="token operator">=</span> i_<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">protected</span><span class="token operator">:</span>
<span class="token keyword">int</span> i<span class="token punctuation">;</span>
<span class="token keyword">mutable</span> std<span class="token double-colon punctuation">::</span>mutex mut<span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>
</code></pre></div><h4 id="remarks"><a href="#remarks" class="header-anchor">#</a> Remarks</h4> <p>Ambiguities can occur when one type can be implicitly converted into more than one type and there is no matching function for that specific type.</p> <p>For example:</p> <div class="language-cpp extra-class"><pre class="language-cpp"><code><span class="token keyword">void</span> <span class="token function">foo</span><span class="token punctuation">(</span><span class="token keyword">double</span><span class="token punctuation">,</span> <span class="token keyword">double</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">void</span> <span class="token function">foo</span><span class="token punctuation">(</span><span class="token keyword">long</span><span class="token punctuation">,</span> <span class="token keyword">long</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">//Call foo with 2 ints</span>
<span class="token function">foo</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//Function call is ambiguous - int can be converted into a double/long at the same time </span>
</code></pre></div></div> <footer class="page-edit"><div class="edit-link"><a href="https://github.com/devtut/generate/edit/master/docs/cpp/function-overloading.md" target="_blank" rel="noopener noreferrer">Edit this page on GitHub</a> <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></div> <!----></footer> <div class="page-nav"><p class="inner"><span class="prev">
←
<a href="/cpp/classes-structures.html" class="prev">
Classes/Structures
</a></span> <span class="next"><a href="/cpp/operator-overloading.html">
Operator Overloading
</a>
→
</span></p></div> </main></div><div class="global-ui"><!----></div></div>
<script src="/assets/js/app.1779e102.js" defer></script><script src="/assets/js/3.2cfa8016.js" defer></script><script src="/assets/js/657.2f669db8.js" defer></script>
</body>
</html>