Conditional Expressions

Detailed Description

Types and operations to defines conditional mask expressions.

Masking lanes from an eve::simd_value is a frequent operations. To simplify and optimize such code, EVE provides objects and functions to define conditions with a high-level of flexibility including: alternative value, index-based relative conditions and more.

See also: Conditional operations

Classes
struct	eve::or_< C, V >
	Conditional/Alternative wrapper. More...
struct	eve::if_< C >
	Extensible wrapper for SIMD conditional. More...
struct	eve::ignore_all_
	Conditional expression selecting no lane from a eve::simd_value. More...
struct	eve::ignore_none_
	Conditional expression selecting all lanes from a eve::simd_value. More...
struct	eve::keep_first
	Conditional expression selecting the k first lanes from a eve::simd_value. More...
struct	eve::ignore_last
	Conditional expression ignoring the k last lanes from a eve::simd_value. More...
struct	eve::keep_last
	Conditional expression keeping the k last lanes from a eve::simd_value. More...
struct	eve::ignore_first
	Conditional expression ignoring the k first lanes from a eve::simd_value. More...
struct	eve::keep_between
	Conditional expression keeping all lanes between two position. More...
struct	eve::ignore_extrema
	Conditional expression ignoring lanes at both extrema of a eve::simd_value. More...

Functions
template<eve::relative_conditional_expr C>
constexpr auto	eve::drop_alternative (C c)
	Returns a conditional without an alternative.
template<eve::relative_conditional_expr C>
auto	eve::map_alternative (C c, auto op)
	Computes a transformed conditional.
template<eve::relative_conditional_expr C, typename Tgt>
auto	eve::bit_cast_alternative (C c, as< Tgt > tgt)
	Computes a transformed conditional.
template<eve::relative_conditional_expr C, typename T>
constexpr auto	eve::reverse_conditional (C c, eve::as< T > tgt)
	Computes the reverse of a given eve::relative_conditional_expr.

Variables
constexpr ignore_all_	eve::ignore_all = {}
	Object representing the eve::ignore_all_ conditional expression.
constexpr ignore_none_	eve::ignore_none = {}
	Object representing the eve::ignore_none_ conditional expression.

Function Documentation

bit_cast_alternative()

template<eve::relative_conditional_expr C, typename Tgt>

auto eve::bit_cast_alternative	(	C	c,
		as< Tgt >	tgt )

Computes a transformed conditional.

Required header: #include <eve/conditional.hpp>

Creates a eve::conditional_expr by bitcasting the alternative value of c to a new type, Tgt, if any is present.

Parameters

c	eve::conditional_expr to transform
tgt	Target type

Returns

A eve::conditional_expr of the same kind that c which alternative value, if any is replaced by the bitcast of c.alternative to Tgt

drop_alternative()

template<eve::relative_conditional_expr C>

auto eve::drop_alternative ( C c )

constexpr

Returns a conditional without an alternative.

Required header: #include <eve/conditional.hpp>

Parameters

c	eve::conditional_expr

map_alternative()

template<eve::relative_conditional_expr C>

auto eve::map_alternative	(	C	c,
		auto	op )

Computes a transformed conditional.

Required header: #include <eve/conditional.hpp>

Creates a eve::conditional_expr by applying an arbitrary operation op on c, thus modifying its alternate value if any is present.

Parameters

c	eve::conditional_expr to transform
op	Unary callable object to apply

Returns

A eve::conditional_expr of the same kind that c which alternative value, if any is replaced by op(c.alternative)

reverse_conditional()

template<eve::relative_conditional_expr C, typename T>

auto eve::reverse_conditional ( C c, eve::as< T > tgt )

constexpr

Computes the reverse of a given eve::relative_conditional_expr.

Required header: #include <eve/conditional.hpp>

For a given eve::relative_conditional_expr c, optimally computes the reverse eve::relative_conditional_expr for a given type T. For example, ignoring the first N lanes get reversed as ignoring the last N lanes.

Parameters

c	Condition to reverse
tgt	Wrapped type of the expected output

Returns

The exact semantic opposite of c with the same internal state.

Example

#include <iostream>
#include <eve/wide.hpp>
#include <eve/conditional.hpp>
 
int main()
{
  std::cout << eve::ignore_all << " -> "
            << eve::reverse_conditional(eve::ignore_all, eve::as(0)) << "\n";
 
  std::cout << eve::ignore_none << " -> "
            << eve::reverse_conditional(eve::ignore_none, eve::as(0)) << "\n";
 
  std::cout << eve::keep_first(1) << " -> "
            << eve::reverse_conditional(eve::keep_first(1), eve::as(0)) << "\n";
 
  std::cout << eve::ignore_last(1) << " -> "
            << eve::reverse_conditional(eve::ignore_last(1), eve::as(0)) << "\n";
}