cpp/string/basic string/npos - Revision history

Ybab321: Undo revision 170898 by Space Mission (talk). Still don't think it's worth the revbox, it's literally impossible to observe the difference

2024-04-14T10:25:14Z

Undo revision 170898 by Space Mission (talk). Still don't think it's worth the revbox, it's literally impossible to observe the difference

← Older revision		Revision as of 10:25, 14 April 2024
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	{{cpp/string/basic_string/title\|npos}}		{{cpp/string/basic_string/title\|npos}}
	{{cpp/string/basic_string/navbar}}		{{cpp/string/basic_string/navbar}}
	{{~~dcl begin}}~~		{{ddcl\|1=
	~~{{dcl rev multi~~\|~~until1=c++23~~
	~~\|dcl1~~=
	static const size_type npos = -1;		static const size_type npos = -1;
	~~\|dcl2=~~
	~~static constexpr size_type npos = size_type(-1);~~
	}}		}}
	~~{{dcl end}}~~

	This is a special value equal to the maximum value representable by the type {{rlpt\|/#Member types\|size_type}}. The exact meaning depends on context, but it is generally used either as end of string indicator by the functions that expect a string index or as the error indicator by the functions that return a string index.		This is a special value equal to the maximum value representable by the type {{rlpt\|/#Member types\|size_type}}. The exact meaning depends on context, but it is generally used either as end of string indicator by the functions that expect a string index or as the error indicator by the functions that return a string index.

Space Mission: /* Synopsis */ formally, `npos` is defined as `constexpr` since C++23 (comparing C++98, ..., C++20 vs C++23 final drafts).

2024-04-13T15:36:50Z

Synopsis: formally, `npos` is defined as `constexpr` since C++23 (comparing C++98, ..., C++20 vs C++23 final drafts).

← Older revision		Revision as of 15:36, 13 April 2024
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	{{cpp/string/basic_string/title\|npos}}		{{cpp/string/basic_string/title\|npos}}
	{{cpp/string/basic_string/navbar}}		{{cpp/string/basic_string/navbar}}
	{{~~ddcl~~\|1=		{{dcl begin}}
			{{dcl rev multi\|until1=c++23
			\|dcl1=
	static const size_type npos = -1;		static const size_type npos = -1;
			\|dcl2=
			static constexpr size_type npos = size_type(-1);
	}}		}}
			{{dcl end}}

	This is a special value equal to the maximum value representable by the type {{rlpt\|/#Member types\|size_type}}. The exact meaning depends on context, but it is generally used either as end of string indicator by the functions that expect a string index or as the error indicator by the functions that return a string index.		This is a special value equal to the maximum value representable by the type {{rlpt\|/#Member types\|size_type}}. The exact meaning depends on context, but it is generally used either as end of string indicator by the functions that expect a string index or as the error indicator by the functions that return a string index.

Ybab321: back to const, npos predates constexpr, and the declarations have identical semantics, so not worth the revbox

2024-04-13T08:38:56Z

back to const, npos predates constexpr, and the declarations have identical semantics, so not worth the revbox

← Older revision		Revision as of 08:38, 13 April 2024
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	{{cpp/string/basic_string/navbar}}		{{cpp/string/basic_string/navbar}}
	{{ddcl\|1=		{{ddcl\|1=
	static ~~constexpr~~ size_type npos = -1;		static const size_type npos = -1;
	}}		}}

Raniarel: AFAIK, `const` is not the same as `constexpr`. Better be precise. See cpp/language/static.

2024-04-13T02:25:10Z

AFAIK, `const` is not the same as `constexpr`. Better be precise. See cpp/language/static.

← Older revision		Revision as of 02:25, 13 April 2024
Line 2:		Line 2:
	{{cpp/string/basic_string/navbar}}		{{cpp/string/basic_string/navbar}}
	{{ddcl\|1=		{{ddcl\|1=
	static ~~const~~ size_type npos = -1;		static constexpr size_type npos = -1;
	}}		}}

Space Mission: /* Example */ ~an alternative (and shorter) way to access `npos`

2023-11-02T06:10:03Z

Example: ~an alternative (and shorter) way to access `npos`

← Older revision		Revision as of 06:10, 2 November 2023
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	// string search functions return npos if nothing is found		// string search functions return npos if nothing is found
	std::string s = "test";		std::string s = "test";
	if (s.find('a') == ~~std::string::~~npos)		if (s.find('a') == s.npos)
	std::cout << "no 'a' in 'test'\n";		std::cout << "no 'a' in 'test'\n";

Ybab321: tbh this just isn't worth mentioning, as hostile implementations don't exist

2023-10-30T12:05:09Z

tbh this just isn't worth mentioning, as hostile implementations don't exist

← Older revision		Revision as of 12:05, 30 October 2023
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	===Note===		===Note===
	Although the definition uses {{c\|-1}}, {{tt\|size_type}} is an unsigned integer type, and the value of {{tt\|npos}} is the largest positive value it can hold, due to [[cpp/language/implicit conversion#Integral conversions\|signed-to-unsigned implicit conversion]]. This is a portable way to specify the largest value of any unsigned type.		Although the definition uses {{c\|-1}}, {{tt\|size_type}} is an unsigned integer type, and the value of {{tt\|npos}} is the largest positive value it can hold, due to [[cpp/language/implicit conversion#Integral conversions\|signed-to-unsigned implicit conversion]]. This is a portable way to specify the largest value of any unsigned type.

	Note that the expression {{c\|std::string::npos {{=}}{{=}} -1}} is not always true. It depends on the relative sizes of the [[cpp/types/size_t\|{{tt\|size_t}}]] type (used by {{tt\|std::string::npos}}) and the [[cpp/language/types\|{{tt\|int}}]] type (used for the literal {{c\|-1}}). If [[cpp/types/size_t\|{{tt\|size_t}}]] is larger or equal in size to [[cpp/language/types\|{{tt\|int}}]], then the expression is true, but if [[cpp/types/size_t\|{{tt\|size_t}}]] is smaller than [[cpp/language/types\|{{tt\|int}}]], it may be false.

	===Example===		===Example===

Ybab321: back to const, npos predates constexpr, and the declarations have identical semantics, so not worth the revbox

2023-10-30T12:00:57Z

back to const, npos predates constexpr, and the declarations have identical semantics, so not worth the revbox

← Older revision		Revision as of 12:00, 30 October 2023
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	{{cpp/string/basic_string/navbar}}		{{cpp/string/basic_string/navbar}}
	{{ddcl\|1=		{{ddcl\|1=
	static ~~constexpr~~ size_type npos = -1;		static const size_type npos = -1;
	}}		}}

Raniarel: Updated the Definition of `npos` (Changed `const` To `constexpr`)

2023-10-30T05:11:44Z

Updated the Definition of `npos` (Changed `const` To `constexpr`)

← Older revision		Revision as of 05:11, 30 October 2023
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	{{cpp/string/basic_string/navbar}}		{{cpp/string/basic_string/navbar}}
	{{ddcl\|1=		{{ddcl\|1=
	static ~~const~~ size_type npos = -1;		static constexpr size_type npos = -1;
	}}		}}

Raniarel: Added Note About Expression std::string::npos == -1

2023-10-30T05:04:57Z

Added Note About Expression std::string::npos == -1

← Older revision		Revision as of 05:04, 30 October 2023
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	===Note===		===Note===
	Although the definition uses {{c\|-1}}, {{tt\|size_type}} is an unsigned integer type, and the value of {{tt\|npos}} is the largest positive value it can hold, due to [[cpp/language/implicit conversion#Integral conversions\|signed-to-unsigned implicit conversion]]. This is a portable way to specify the largest value of any unsigned type.		Although the definition uses {{c\|-1}}, {{tt\|size_type}} is an unsigned integer type, and the value of {{tt\|npos}} is the largest positive value it can hold, due to [[cpp/language/implicit conversion#Integral conversions\|signed-to-unsigned implicit conversion]]. This is a portable way to specify the largest value of any unsigned type.

			Note that the expression {{c\|std::string::npos {{=}}{{=}} -1}} is not always true. It depends on the relative sizes of the [[cpp/types/size_t\|{{tt\|size_t}}]] type (used by {{tt\|std::string::npos}}) and the [[cpp/language/types\|{{tt\|int}}]] type (used for the literal {{c\|-1}}). If [[cpp/types/size_t\|{{tt\|size_t}}]] is larger or equal in size to [[cpp/language/types\|{{tt\|int}}]], then the expression is true, but if [[cpp/types/size_t\|{{tt\|size_t}}]] is smaller than [[cpp/language/types\|{{tt\|int}}]], it may be false.

	===Example===		===Example===

Space Mission: ~link to size_type

2023-07-13T17:08:07Z

~link to size_type

← Older revision		Revision as of 17:08, 13 July 2023
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	}}		}}

	This is a special value equal to the maximum value representable by the type {{tt\|size_type}}. The exact meaning depends on context, but it is generally used either as end of string indicator by the functions that expect a string index or as the error indicator by the functions that return a string index.		This is a special value equal to the maximum value representable by the type {{rlpt\|/#Member types\|size_type}}. The exact meaning depends on context, but it is generally used either as end of string indicator by the functions that expect a string index or as the error indicator by the functions that return a string index.

	===Note===		===Note===
	Although the definition uses {{c\|-1}}, {{~~ltt\|cpp/string/basic_string~~\|size_type}} is an unsigned integer type, and the value of {{tt\|npos}} is the largest positive value it can hold, due to [[cpp/language/implicit conversion#Integral conversions\|signed-to-unsigned implicit conversion]]. This is a portable way to specify the largest value of any unsigned type.		Although the definition uses {{c\|-1}}, {{tt\|size_type}} is an unsigned integer type, and the value of {{tt\|npos}} is the largest positive value it can hold, due to [[cpp/language/implicit conversion#Integral conversions\|signed-to-unsigned implicit conversion]]. This is a portable way to specify the largest value of any unsigned type.

	===Example===		===Example===