90 lines
3.8 KiB
Markdown
90 lines
3.8 KiB
Markdown
[template.mask.array]
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# 29 Numerics library [[numerics]](./#numerics)
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## 29.6 Numeric arrays [[numarray]](numarray#template.mask.array)
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### 29.6.8 Class template mask_array [template.mask.array]
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#### [29.6.8.1](#overview) Overview [[template.mask.array.overview]](template.mask.array.overview)
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[ð](#lib:mask_array)
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namespace std {template<class T> class mask_array {public:using value_type = T; void operator= (const valarray<T>&) const; void operator*= (const valarray<T>&) const; void operator/= (const valarray<T>&) const; void operator%= (const valarray<T>&) const; void operator+= (const valarray<T>&) const; void operator-= (const valarray<T>&) const; void operator^= (const valarray<T>&) const; void operator&= (const valarray<T>&) const; void operator|= (const valarray<T>&) const; void operator<<=(const valarray<T>&) const; void operator>>=(const valarray<T>&) const;
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mask_array(const mask_array&); ~mask_array(); const mask_array& operator=(const mask_array&) const; void operator=(const T&) const;
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mask_array() = delete; // as implied by declaring copy constructor above};}
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[1](#overview-1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L8913)
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This template is a helper template used by the mask subscript operator:
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[ð](#lib:operator%5b%5d,mask_array)
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`mask_array<T> valarray<T>::operator[](const valarray<bool>&);
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`
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[2](#overview-2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L8920)
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It has reference semantics to a subset of an array specified by a boolean mask[.](#overview-2.sentence-1)
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Thus, the expression a[mask] = b; has the effect of assigning the elements ofb to the masked elements in a (those for which the corresponding element inmask is true)[.](#overview-2.sentence-2)
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#### [29.6.8.2](#mask.array.assign) Assignment [[mask.array.assign]](mask.array.assign)
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[ð](#lib:operator=,mask_array)
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`void operator=(const valarray<T>&) const;
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const mask_array& operator=(const mask_array&) const;
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`
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[1](#mask.array.assign-1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L8937)
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These assignment operators have reference semantics, assigning the values
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of the argument array elements to selected elements of thevalarray<T> object to which the mask_array object refers[.](#mask.array.assign-1.sentence-1)
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#### [29.6.8.3](#mask.array.comp.assign) Compound assignment [[mask.array.comp.assign]](mask.array.comp.assign)
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[ð](#lib:operator*=,mask_array)
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`void operator*= (const valarray<T>&) const;
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void operator/= (const valarray<T>&) const;
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void operator%= (const valarray<T>&) const;
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void operator+= (const valarray<T>&) const;
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void operator-= (const valarray<T>&) const;
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void operator^= (const valarray<T>&) const;
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void operator&= (const valarray<T>&) const;
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void operator|= (const valarray<T>&) const;
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void operator<<=(const valarray<T>&) const;
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void operator>>=(const valarray<T>&) const;
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`
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[1](#mask.array.comp.assign-1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L8970)
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These compound assignments have reference semantics, applying the
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indicated operation to the elements of the argument array and selected elements
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of thevalarray<T> object to which the mask_array object refers[.](#mask.array.comp.assign-1.sentence-1)
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#### [29.6.8.4](#mask.array.fill) Fill function [[mask.array.fill]](mask.array.fill)
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[ð](#lib:operator=,mask_array_)
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`void operator=(const T&) const;
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`
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[1](#mask.array.fill-1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L8986)
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This function has reference semantics, assigning the value of its
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argument to the elements of thevalarray<T> object to which themask_array object refers[.](#mask.array.fill-1.sentence-1)
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