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Difference between revisions of "cpp/numeric/ratio/ratio equal"

From cppreference.com
< cpp‎ | numeric‎ | ratio
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{{cpp/title | ratio_equal}}
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{{cpp/title|ratio_equal}}
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{{cpp/numeric/ratio/sidebar}}
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{{cpp/numeric/ratio/}}
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{{ddcl list begin}}
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{{ddclheader||1=
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{{ddcl list header | ratio}}
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{{ddcl list item | 1=
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template< class R1, class R2 >
 
template< class R1, class R2 >
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struct ratio_equal : std::integral_constant;
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struct ratio_equal : std::integral_constant;
 
}}
 
}}
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{{ddcl list end}}
 
  
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If the ratios R1 and R2 are equal, provides the member constant {{tt|value}} equal {{cpp|true}}. Otherwise, {{tt|value}} is {{cpp|false}}.
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If the ratios R1and R2are equal, provides the member constant {{|value}} equal {{|true}}. Otherwise, {{|value}} is {{|false}}.
  
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{{cpp/types/integral_constant/inherit | {{cpp|1=R1::num == R2::num && R1::den == R2::den}} }}
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{{cpp/types/integral_constant/inherit|{{|1=R1::num == R2::num && R1::den == R2::den}}}}
  
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===Equivalent definition===
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======
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{{eq fun cpp
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{{eq fun
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| 1=
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|1=
 
template< class R1, class R2 >
 
template< class R1, class R2 >
 
struct ratio_equal : public std::integral_constant <
 
struct ratio_equal : public std::integral_constant <
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===Example===
 
===Example===
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{{example cpp
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{{example
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|
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|code=
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| code=
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#include <iostream>
 
#include <iostream>
 
#include <ratio>
 
#include <ratio>
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int main()
 
int main()
 
{
 
{
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     if(std::ratio_equal<std::ratio<2,3>, std::ratio<4,6>>::value)
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     std::<std::ratio<2,3>,
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        std::cout << "2/3 == 4/6\n";
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std::ratio<6>>
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    else
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)
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        std::cout << "2/3 != 4/6\n";
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std::cout << "2/3 ==" : "!=6\n";
 
}
 
}
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| output=
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|output=
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2/3 == 4/6
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2/3 == 6
 
}}
 
}}
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 +
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Latest revision as of 15:46, 24 September 2024

 
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Compile-time rational arithmetic
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ratio_equal
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(C++11)
 
Defined in header <ratio>
template< class R1, class R2 >
struct ratio_equal : std::integral_constant<bool, /* see below */> { };
 (since C++11)

If the ratios R1 and R2 are equal, provides the member constant value equal true. Otherwise, value is false.

Contents

[edit] Helper variable template

template< class R1, class R2 >
constexpr bool ratio_equal_v = ratio_equal<R1, R2>::value;
 (since C++17)
[edit]

Inherited from std::integral_constant

Member constants

value
[static]
 true if R1::num == R2::num && R1::den == R2::den, false otherwise
(public static member constant)

Member functions

operator bool
 converts the object to bool, returns value
(public member function)
operator()
(C++14)
 returns value
(public member function)

Member types

Type Definition
value_type bool
type std::integral_constant<bool, value>

[edit] Possible implementation

template< class R1, class R2 >
struct ratio_equal : public std::integral_constant <
                                 bool,
                                 R1::num == R2::num && R1::den == R2::den
                            > {};

[edit] Example

Run this code
#include <iostream>
#include <ratio>
 
int main()
{
    constexpr bool equ = std::ratio_equal_v<std::ratio<2,3>,
                                            std::ratio<6,9>>;
    static_assert(equ);
    std::cout << "2/3 " << (equ ? "==" : "!=") << " 6/9\n";
}

Output: 

2/3 == 6/9

[edit] See also

(C++11)
 compares two ratio objects for inequality at compile-time
(class template) [edit]
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