Does the C++ standard require operator != must be provided for a given iterator type?
The C++17 standard 27.2.1.8 says:
An iterator j is called reachable from an iterator i if and only if
there is a finite sequence of applications of the expression ++i that
makes i == j.
That is to say, any conforming iterator type must provide operator ==.
However, I find nothing about operator != is a requirement for iterator types.
Does the C++ standard require operator != must be provided for a given iterator type?
c++ iterator standards semantics typetraits
asked Nov 28 '18 at 3:34
xmllmxxmllmx
13.9k988212
add a comment |
The C++17 standard 27.2.1.8 says:
An iterator j is called reachable from an iterator i if and only if
there is a finite sequence of applications of the expression ++i that
makes i == j.
That is to say, any conforming iterator type must provide operator ==.
However, I find nothing about operator != is a requirement for iterator types.
Does the C++ standard require operator != must be provided for a given iterator type?
c++ iterator standards semantics typetraits
asked Nov 28 '18 at 3:34
xmllmxxmllmx
13.9k988212
3
"That is to say, any conforming iterator type must provide operator ==." That's not where the requirement foroperator==is spelled out. Requirements tend to be in tables.
– Nicol Bolas
Nov 28 '18 at 3:44
add a comment |
The C++17 standard 27.2.1.8 says:
An iterator j is called reachable from an iterator i if and only if
there is a finite sequence of applications of the expression ++i that
makes i == j.
That is to say, any conforming iterator type must provide operator ==.
However, I find nothing about operator != is a requirement for iterator types.
Does the C++ standard require operator != must be provided for a given iterator type?
c++ iterator standards semantics typetraits
asked Nov 28 '18 at 3:34
xmllmxxmllmx
13.9k988212
The C++17 standard 27.2.1.8 says:
An iterator j is called reachable from an iterator i if and only if
there is a finite sequence of applications of the expression ++i that
makes i == j.
That is to say, any conforming iterator type must provide operator ==.
However, I find nothing about operator != is a requirement for iterator types.
Does the C++ standard require operator != must be provided for a given iterator type?
c++ iterator standards semantics typetraits
c++ iterator standards semantics typetraits
asked Nov 28 '18 at 3:34
xmllmxxmllmx
13.9k988212
asked Nov 28 '18 at 3:34
xmllmxxmllmx
13.9k988212
edited Nov 28 '18 at 4:16
xmllmx
asked Nov 28 '18 at 3:34
xmllmxxmllmx
13.9k988212
asked Nov 28 '18 at 3:34
xmllmxxmllmx
13.9k988212
asked Nov 28 '18 at 3:34
xmllmxxmllmx
13.9k988212
13.9k988212
3
"That is to say, any conforming iterator type must provide operator ==." That's not where the requirement foroperator==is spelled out. Requirements tend to be in tables.
– Nicol Bolas
Nov 28 '18 at 3:44
add a comment |
3
"That is to say, any conforming iterator type must provide operator ==." That's not where the requirement foroperator==is spelled out. Requirements tend to be in tables.
– Nicol Bolas
Nov 28 '18 at 3:44
3
3
"That is to say, any conforming iterator type must provide operator ==." That's not where the requirement for
operator== is spelled out. Requirements tend to be in tables.– Nicol Bolas
Nov 28 '18 at 3:44
"That is to say, any conforming iterator type must provide operator ==." That's not where the requirement for
operator== is spelled out. Requirements tend to be in tables.– Nicol Bolas
Nov 28 '18 at 3:44
add a comment |
1 Answer
1
active
oldest
votes
See C++17 [input.iterators]/2 Table 95 "Input iterator requirements".
Input iterators require that a != b is valid and behaves the same as !(a == b) if the latter is valid. Link to cppreference.com summary
Output iterators do not need to support either operation.
answered Nov 28 '18 at 3:40
M.MM.M
106k11119242
It looks like it's table 95 in n4659, which is supposed to be the same as the C++17 standard except minor editorial changes. Is that a typo, or did "minor editorial changes" really change the numbering by 19 places? Also, here's a link to the relevant part of an HTML version of n4659.
– Daniel H
Nov 28 '18 at 4:23
@DanielH thanks, I'd accidentally loaded up a later draft
– M.M
Nov 28 '18 at 4:27
add a comment |
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1 Answer
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1 Answer
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active
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votes
See C++17 [input.iterators]/2 Table 95 "Input iterator requirements".
Input iterators require that a != b is valid and behaves the same as !(a == b) if the latter is valid. Link to cppreference.com summary
Output iterators do not need to support either operation.
answered Nov 28 '18 at 3:40
M.MM.M
106k11119242
It looks like it's table 95 in n4659, which is supposed to be the same as the C++17 standard except minor editorial changes. Is that a typo, or did "minor editorial changes" really change the numbering by 19 places? Also, here's a link to the relevant part of an HTML version of n4659.
– Daniel H
Nov 28 '18 at 4:23
@DanielH thanks, I'd accidentally loaded up a later draft
– M.M
Nov 28 '18 at 4:27
add a comment |
See C++17 [input.iterators]/2 Table 95 "Input iterator requirements".
Input iterators require that a != b is valid and behaves the same as !(a == b) if the latter is valid. Link to cppreference.com summary
Output iterators do not need to support either operation.
answered Nov 28 '18 at 3:40
M.MM.M
106k11119242
It looks like it's table 95 in n4659, which is supposed to be the same as the C++17 standard except minor editorial changes. Is that a typo, or did "minor editorial changes" really change the numbering by 19 places? Also, here's a link to the relevant part of an HTML version of n4659.
– Daniel H
Nov 28 '18 at 4:23
@DanielH thanks, I'd accidentally loaded up a later draft
– M.M
Nov 28 '18 at 4:27
add a comment |
See C++17 [input.iterators]/2 Table 95 "Input iterator requirements".
Input iterators require that a != b is valid and behaves the same as !(a == b) if the latter is valid. Link to cppreference.com summary
Output iterators do not need to support either operation.
answered Nov 28 '18 at 3:40
M.MM.M
106k11119242
See C++17 [input.iterators]/2 Table 95 "Input iterator requirements".
Input iterators require that a != b is valid and behaves the same as !(a == b) if the latter is valid. Link to cppreference.com summary
Output iterators do not need to support either operation.
answered Nov 28 '18 at 3:40
M.MM.M
106k11119242
edited Nov 28 '18 at 4:26
answered Nov 28 '18 at 3:40
M.MM.M
106k11119242
answered Nov 28 '18 at 3:40
M.MM.M
106k11119242
answered Nov 28 '18 at 3:40
M.MM.M
106k11119242
106k11119242
It looks like it's table 95 in n4659, which is supposed to be the same as the C++17 standard except minor editorial changes. Is that a typo, or did "minor editorial changes" really change the numbering by 19 places? Also, here's a link to the relevant part of an HTML version of n4659.
– Daniel H
Nov 28 '18 at 4:23
@DanielH thanks, I'd accidentally loaded up a later draft
– M.M
Nov 28 '18 at 4:27
add a comment |
It looks like it's table 95 in n4659, which is supposed to be the same as the C++17 standard except minor editorial changes. Is that a typo, or did "minor editorial changes" really change the numbering by 19 places? Also, here's a link to the relevant part of an HTML version of n4659.
– Daniel H
Nov 28 '18 at 4:23
@DanielH thanks, I'd accidentally loaded up a later draft
– M.M
Nov 28 '18 at 4:27
It looks like it's table 95 in n4659, which is supposed to be the same as the C++17 standard except minor editorial changes. Is that a typo, or did "minor editorial changes" really change the numbering by 19 places? Also, here's a link to the relevant part of an HTML version of n4659.
– Daniel H
Nov 28 '18 at 4:23
It looks like it's table 95 in n4659, which is supposed to be the same as the C++17 standard except minor editorial changes. Is that a typo, or did "minor editorial changes" really change the numbering by 19 places? Also, here's a link to the relevant part of an HTML version of n4659.
– Daniel H
Nov 28 '18 at 4:23
@DanielH thanks, I'd accidentally loaded up a later draft
– M.M
Nov 28 '18 at 4:27
@DanielH thanks, I'd accidentally loaded up a later draft
– M.M
Nov 28 '18 at 4:27
add a comment |
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3
"That is to say, any conforming iterator type must provide operator ==." That's not where the requirement for
operator==is spelled out. Requirements tend to be in tables.– Nicol Bolas
Nov 28 '18 at 3:44