tmp/tmphglon4xf/{from.md → to.md}
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## Qualification conversions <a id="conv.qual">[[conv.qual]]</a>
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“*cv1* `T`”.
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``` cpp
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int main() {
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const char c = 'c';
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char* pc;
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@@ -27,21 +47,17 @@ int main() {
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*pcc = &c;
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*pc = 'C'; // #2: modifies a const object
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}
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```
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and pointer to member type has the form:
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type *T* and integer n > 0 such that:
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and
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For similar multi-level pointer to member types and similar multi-level
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mixed pointer and pointer to member types, the rules for adding
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cv-qualifiers are the same as those used for similar pointer types.
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## Qualification conversions <a id="conv.qual">[[conv.qual]]</a>
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A *cv-decomposition* of a type `T` is a sequence of cvᵢ and Pᵢ such that
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`T` is
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where each cvᵢ is a set of cv-qualifiers ([[basic.type.qualifier]]),
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and each Pᵢ is “pointer to” ([[dcl.ptr]]), “pointer to member of class
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Cᵢ of type” ([[dcl.mptr]]), “array of Nᵢ”, or “array of unknown bound
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of” ([[dcl.array]]). If Pᵢ designates an array, the cv-qualifiers cvᵢ₊₁
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on the element type are also taken as the cv-qualifiers cvᵢ of the
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array.
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[*Example 1*: The type denoted by the *type-id* `const int **` has two
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cv-decompositions, taking `U` as “`int`” and as “pointer to
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`const int`”. — *end example*]
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The n-tuple of cv-qualifiers after the first one in the longest
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cv-decomposition of `T`, that is, cv₁, cv₂, …, cvₙ, is called the
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*cv-qualification signature* of `T`.
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Two types `T₁` and `T₂` are *similar* if they have cv-decompositions
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with the same n such that corresponding Pᵢ components are the same and
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the types denoted by `U` are the same.
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A prvalue expression of type `T₁` can be converted to type `T₂` if the
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following conditions are satisfied, where cvᵢʲ denotes the cv-qualifiers
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in the cv-qualification signature of `Tⱼ`: [^4]
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- `T₁` and `T₂` are similar.
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- For every i > 0, if `const` is in cvᵢ¹ then `const` is in cvᵢ², and
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similarly for `volatile`.
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- If the cvᵢ¹ and cvᵢ² are different, then `const` is in every cvₖ² for
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0 < k < i.
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[*Note 1*:
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If a program could assign a pointer of type `T**` to a pointer of type
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`const` `T**` (that is, if line \#1 below were allowed), a program could
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inadvertently modify a `const` object (as it is done on line \#2). For
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example,
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``` cpp
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int main() {
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const char c = 'c';
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char* pc;
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*pcc = &c;
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*pc = 'C'; // #2: modifies a const object
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}
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```
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— *end note*]
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[*Note 2*: A prvalue of type “pointer to *cv1* `T`” can be converted to
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a prvalue of type “pointer to *cv2* `T`” if “*cv2* `T`” is more
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cv-qualified than “*cv1* `T`”. A prvalue of type “pointer to member of
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`X` of type *cv1* `T`” can be converted to a prvalue of type “pointer to
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member of `X` of type *cv2* `T`” if “*cv2* `T`” is more cv-qualified
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than “*cv1* `T`”. — *end note*]
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[*Note 3*: Function types (including those used in pointer to member
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function types) are never cv-qualified ([[dcl.fct]]). — *end note*]
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