tmp/tmpjv20dq9k/{from.md → to.md}
RENAMED
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@@ -26,25 +26,24 @@ where
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- if the *for-range-initializer* is an *expression*, it is regarded as
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if it were surrounded by parentheses (so that a comma operator cannot
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be reinterpreted as delimiting two *init-declarator*s);
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- *`range`*, *`begin`*, and *`end`* are variables defined for exposition
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only; and
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- *begin-expr* and *end-expr* are determined as follows:
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- if the *for-range-initializer* is an expression of array type `R`,
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*begin-expr* and *end-expr* are *`range`* and *`range`* `+` `N`,
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respectively, where `N` is the array bound. If `R` is an array of
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unknown bound or an array of incomplete type, the program is
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ill-formed;
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- if the *for-range-initializer* is an expression of class type `C`,
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-
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-
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-
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declaration, *begin-expr* and *end-expr* are `range.begin()` and
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`range.end()`, respectively;
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- otherwise, *begin-expr* and *end-expr* are `begin(range)` and
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`end(range)`, respectively, where `begin` and `end`
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-
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\[*Note 1*: Ordinary unqualified lookup [[basic.lookup.unqual]] is
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not performed. — *end note*]
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[*Example 1*:
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@@ -54,9 +53,29 @@ for (int& x : array)
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x *= 2;
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```
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— *end example*]
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In the *decl-specifier-seq* of a *for-range-declaration*, each
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*decl-specifier* shall be either a *type-specifier* or `constexpr`. The
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*decl-specifier-seq* shall not define a class or enumeration.
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- if the *for-range-initializer* is an *expression*, it is regarded as
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if it were surrounded by parentheses (so that a comma operator cannot
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be reinterpreted as delimiting two *init-declarator*s);
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- *`range`*, *`begin`*, and *`end`* are variables defined for exposition
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only; and
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+
- *`begin-expr`* and *`end-expr`* are determined as follows:
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- if the *for-range-initializer* is an expression of array type `R`,
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*`begin-expr`* and *`end-expr`* are *`range`* and *`range`* `+` `N`,
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respectively, where `N` is the array bound. If `R` is an array of
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unknown bound or an array of incomplete type, the program is
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ill-formed;
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- if the *for-range-initializer* is an expression of class type `C`,
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and searches in the scope of `C` [[class.member.lookup]] for the
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names `begin` and `end` each find at least one declaration,
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*`begin-expr`* and *`end-expr`* are `range.begin()` and
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`range.end()`, respectively;
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- otherwise, *`begin-expr`* and *`end-expr`* are `begin(range)` and
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`end(range)`, respectively, where `begin` and `end` undergo
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argument-dependent lookup [[basic.lookup.argdep]].
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\[*Note 1*: Ordinary unqualified lookup [[basic.lookup.unqual]] is
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not performed. — *end note*]
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[*Example 1*:
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x *= 2;
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```
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— *end example*]
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[*Note 2*: The lifetime of some temporaries in the
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*for-range-initializer* is extended to cover the entire loop
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[[class.temporary]]. — *end note*]
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+
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[*Example 2*:
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+
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``` cpp
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using T = std::list<int>;
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const T& f1(const T& t) { return t; }
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const T& f2(T t) { return t; }
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T g();
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void foo() {
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for (auto e : f1(g())) {} // OK, lifetime of return value of g() extended
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for (auto e : f2(g())) {} // undefined behavior
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}
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```
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— *end example*]
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In the *decl-specifier-seq* of a *for-range-declaration*, each
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*decl-specifier* shall be either a *type-specifier* or `constexpr`. The
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*decl-specifier-seq* shall not define a class or enumeration.
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