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Artifact ID: | 1860bc759b2c9ffa0e75bcc18b1a282c360587ec |
---|---|

Page Name: | IndependentFeatures |

Date: | 2017-12-24 19:03:51 |

Original User: | luismachuca |

Parent: | 679f10a86897e81fa625d6e402574f75aa88266c |

# Cxxomfort Library Utilities

The `cxxomfort`

library offers some specific utilities of its own, not found in C++03 or C++11.

The header `cxxomfort/library.hpp>`

is responsible for adding these features, and automatically included when using `#include <cxxomfort/cxxomfort.hpp>`

as well. All the features thus included are defined in namespace `cxxomfort`

.

Unlike Features/Extras, these features are considered intrinsic to the cxxomfort library: other features are allowed to depend on them, and they do not need to be explicitly included to work.

**General index of library utilities**:

- Supplementals for <algorithm>
- Supplementals for <functional>
- Supplementals for <iterator>
- Supplementals for <random>
- Supplementals for <string>
- Supplementals for <tuple>
- Foreach Loop Emulation
`fixed_vector`

- Initialization of sequences
- Local Function Emulation
- Movable
`pair`

- Type Identification utilities
- Typesafe Enums

## Foreach Loop

**"foreach" Loop emulation**: allows writing C++11-like foreach loops in C++03 via a reworked implementation of the Artima *Foreach* utility, which also generates native foreach loops in C++11 onwards, thus resulting in zero overhead.

Sequence<string> mystrings; // fill mystrings somehow CXXO_FOREACH /string const& s, mystrings) { .... }

## Fixed_vector

** fixed_vector<T>** - the oft sought for holy grail of a

`std::vector`

whose size is fixed at construction as an invariant.
## Initialization of Sequence Containers

**Initialization of Sequences**: a way to use a syntax similar to C++11's `{ , , , }`

initialization of containers in various kinda of sequence-like containers, even in C++03.

typedef vector<string> VS_t; CXXO_I12N_SEQ (VS_t, mystrings, { "foo", "bar", "baz" } ); // operate on mystrings cout<< mystrings[1]<< endl;

## Local Function Emulation

**Using local functions in template calls**: a way to have locally defined functions or functors, which then can be used as arguments for eg.: STL algorithm calls. While one of the big limitations in C++03 is the inability to use *local types* as arguments to anything templated, this library adds a partial implementation that creates proxy functor objects, where the actual "calling" code resides out of scope, and that produces code near transpartent to C++11 onwards.

// here, X is a tag that identifies the functor type in case one needs to add state or other nontrivial behaviour CXXO_LOCALFN(X,void(int,int)) (int x0, int x1) { std::cout<< '{'<< x0+1<< ','<< x1-1<< '}'<< std::endl; } CXXO_LOCALFN_NAME(X,mi_fn); function<void(int,int)> f_localfn = mi_fn; // <-- can only exist in the current scope CXXO_LOCALFN(Neg_,int(int)) (int x) { return -x; } CXXO_LOCALFN_NAME(Neg_,negate); transform( begin(sequence), end(sequence), begin(sequence), negate );

## Type Identification

`std::string`

**typeid_demangle**(std::type_info const&)

Given an argument resulting from *typeid* evaluation, returns the same information as `typeid::name()`

, except this information is demangled if demangling is available.

`template <type_name`

**T**>

std::string**type_name**()

Given a template argument type, this returns the same information as the above, except this takes into consideration cv-qualifiers and, in C++11, reference types, that are usually missed by `typeid`

.

## Typesafe Enums

** typesafe_enum<T,S>** - a typesafe declaration wrapper for enum types, that implements the basic idea behind the

`enum class...`

feature of C++11.
## Supplemental Headers

### Supplemental Algorithms for <algorithm>

As a supplement to the features of C++ Standards available in `<algorithm>`

, cxxomfort provides a number of algorithms and generics of its own make available from `<cxxomfort/library/algorithmfn.hpp>`

.

`accumulate_separate`

- accumulates elements over a range, including a selected "separator" element over each iteration.`count_frequencies`

- counts elements in a range, keeping count of each separate value found in an external indexable range.`count_while`

- iterates over the elements of a range, keeping a count of iterations.`find_last_if`

- finds the last element in a range that fulfills a predicate.`transform_inplace`

- three-argument version of`transform`

that transforms the same range being iterated.`transform_n`

- the "_n" counterpart to transform as copy_n is to copy.

### Supplemental Utilities for <functional>

As a supplement to the features of C++ Standards available in `<functional>`

, cxxomfort provides a number of functional apparatuses of its own make available from `<cxxomfort/library/functionalfn.hpp>`

and `<cxxomfort/library/operatorit.hpp>`

.

**Functional supplements to operator wrappers** - Just as there exists `std::plus`

to wrap `operator+`

, cxxomfort provides wrappers for the assignment version of those operators.

`plus_it`

- applies "`+=`

" to its arguments.`minus_it`

- applies "`-=`

" to its arguments.`multiplies_it`

- applies "`*=`

" to its arguments.`divides_it`

- applies "`/=`

" to its arguments.`modulus_it`

- applies "`%=`

" to its arguments.

### Supplemental Utilities for <iterator>

As a supplement to the features of C++ Standards available in `<iterator>`

, cxxomfort provides a number of algorithms and generics of its own make available from `<cxxomfort/library/iteratorfn.hpp>`

.

`fake_iterator`

- an iterator that does not "iterate" anywhere, and is just dereferenciable to a given object. Basically a synonym for "constant_iterator".

### Supplemental String Utilities

As a supplement to the features of C++ Standards available in `<string>`

, cxxomfort provides a number of algorithms and generics of its own make available from `<cxxomfort/library/stringfn.hpp>`

.

- The variadic form of
`to_string`

as suggested by p0117r0. - Similes to the PHP functions "implode" and "explode", for joining and splitting strings.

### Supplemental Tuple Utilities

As a supplement to the features of C++ Standards available in `<tuple>`

, cxxomfort provides a number of algorithms and generics of its own make available from `<cxxomfort/library/tuplefn.hpp>`

.

`is_tuple`

- type trait to recognize a tuple.`tuple_pop`

- creates a tuple with the last (rightmost) element removed.`tuple_shift`

- creates a tuple with the first (leftmost) element removed (C++11 onwards only).`tuple2function_t`

- creates a function signature type (`R(T1,T2,...)`

) according to a list of tuple arguments (`tuple<T1,T2,...>`

).`function2tuple_t`

- the inverse of the above.

### Supplemental Type Traits

`is_iterator`

- to recognize an iterator.`is_std_function`

- to recognize a`std::function`

.`is_pair`

- to recognize a`std::pair`

(in C++03, also a`cxxomfort::pair`

).`is_tuple`

- to recognize a`std::tuple`

.

Given a type *T*, the trait `is_iterator`

inherits from `std::true_type`

if:

- there exists a specialization of
`std::iterator_traits`

for the given T. - Alternatively, T is a non-void pointer type.

Given a type *T*, the trait `is_pair`

inherits from `std::true_type`

if:

- T is a
`std::pair`

. - (C++03 only) T is a
`cxxomfort::pair`

.

Similarly, `is_tuple`

inherits from the true type if:

- T is a
`std::tuple`

. - Alternatively, in C++03 mode, T is a
`std::tr1::tuple`

with up to 10 elements, or more if the compiler supports variadic templates in "emulation" mode.

### Supplemental Utilities

## Other Features

The following traits are available in `cxxomfort/utilities.hpp`

as assistance when writing generic / quasi-generic code.

`is_any_of`

Given a type *T* and a list of types *A1, A2, …, A9*, the trait `is_any_of<T, A1, A2, …, A9>`

inherits from `std::true_type`

if:

- T is an exact
__cv-qualified match__for any of the types A1, A2, …, A9.

In both C++03 and C++11, this trait can take up to 10 candidate types.

`is_sequence`

Given a type *T*, the trait `is_sequence`

inherits from `std::true_type`

if:

- T defines both a
`::const_iterator`

and a`::value_type`

member types. - Alternatively, T is a native C array of known bounds (ie.: a
`T(&)[N]`

for a known N).

`function_arity`

Given a type *T*, the trait `function_arity<T>`

inherits from `std::integral_constant<size_t, N>`

for N to-be-determined below, if:

- T is a type signature of a function type eg.:
`T = R(A1, A2, …)`

. In this case,`N`

is equal to the number of function arguments in the signature type. - T is a
`std::function`

for a given type signature of the above. In this case,`N`

is equal to the number of function arguments in the signature type. - T is a
`std::pointer_to_unary_function`

. In this case,`N= 1`

. - T is a
`std::pointer_to_binary_function`

. In this case,`N=2`

. - (
**Not implemented yet**) T is a generator type based off the templates`linear_congruential_engine`

,`substract_with_carry_engine`

or`mersenne_twister_engine`

, or the type`random_device`

. In this case,`N=0`

.

In C++03 mode, this trait can recognize function types up to 10 arguments.

If *T* is none of the above, an instantiation of `function_arity`

results in an error.

`result_of_function`

Given a type *T*, the trait `result_of_function<T>`

defines the member type `::type`

, as a type to-be-determined below, if:

- T is a type signature of a function type eg.:
`T = R(A1,A2, …)`

. In this case,`type: R`

. - T is a pointer type to the above eg.:
`T = R(*)(A1,A2,…)`

. In this case,`type`

is defined as in the above. - (
**Not implemented yet**) T is`std::random_device`

. In this case,`type: unsigned int`

.

In C++03 mode, this trait can recognize function types up to 10 arguments.

`integral_of_size`

Given a compile-time integer *N*, with `N≥0`

, this trait defines the member type `::type`

, as a type to-be-determined-below, if:

- There exists a native signed integral type
*I*such that`sizeof(I)==N`

. In this case,`type: I`

.

If there is no integral type for the given value of *N*, instantiation of this template results in an error.

### Utility Functions

`null_device`

This trait defines the static member variable `const char* value`

as the literal string corresponding to the "null device" recognized by the OS in the current compiler.

- Under POSIX, this is
`"/dev/null"`

- Under Microsoft Windows, this is
`"NUL"`

. - Under other systems this is left a null-string.

----

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