How to resolve the algorithm Named parameters step by step in the C++ programming language

Published on 7 June 2024 03:52 AM
#cpp

How to resolve the algorithm Named parameters step by step in the C++ programming language

Table of Contents

Problem Statement

Create a function which takes in a number of arguments which are specified by name rather than (necessarily) position, and show how to call the function. If the language supports reordering the arguments or optionally omitting some of them, note this. Note: See also:

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Named parameters step by step in the C++ programming language

1. Named Parameters (Custom Parameterized Class):

  • Custom class foo_params allows defining parameters with names and default values.
  • Constructors and chainable member functions (x(int), y(int), z(float)) set parameter values.

Example:

foo(foo_params(42).x(7).z(23.54));

2. Boost Parameter Library for Named Parameters:

  • Boost provides a generic solution for parameterizing functions with named arguments.
  • The BOOST_PARAMETER_NAME and BOOST_PARAMETER_FUNCTION macros are used to define named parameters for functions.

Example:

BOOST_PARAMETER_FUNCTION(
   function_with_named_parameters,
   (required (foo, (int)) (bar, (float)))
   (optional (baz, (bool), false) (bonk, (std::string), "default value"))
)

3. Using Named Parameters:

  • You can call functions with named parameters by passing their values as key-value pairs, e.g.:
function_with_named_parameters(1, 10.0);
function_with_named_parameters(_bar = 3.14, _foo = 7);
  • You can pass some parameters positionally and others by name, e.g.:
function_with_named_parameters(9, _bar = 2.5, _bonk = "Hello", _foo = 42);

Benefits of Named Parameters:

  • Improved Code Readability: Parameters are clearly named, making the code easier to understand.
  • Reduced Error Prone: The use of named parameters eliminates potential errors caused by mismatching types or ordering.
  • Enhanced Flexibility: Named parameters allow for optional parameters and customizable function behavior.
  • Extensibility: You can add new parameters as needed without breaking existing code that uses only a subset of them.

Source code in the cpp programming language

class foo_params{
	friend void foo(foo_params p);
public:
    foo_params(int r):
        required_param_(r),
	optional_x_(0),
	optional_y_(1),
	optional_z_(3.1415)
	{}
     foo_params& x(int i){
	optional_x_=i;
	return *this;
     }
     foo_params& y(int i){
	optional_y_=i;
	return *this;
     }
     foo_params& z(float f){
	optional_z_=f;
	return *this;
     }
private:
        int 	required_param_;
	int 	optional_x_;
	int 	optional_y_;
	float 	optional_z_;
};


void foo(foo_params p){ . . .}


foo(foo_params(42).x(7).z(23.54));


#include <boost/parameter/name.hpp>
#include <boost/parameter/preprocessor.hpp>
#include <string>

BOOST_PARAMETER_NAME(foo)
BOOST_PARAMETER_NAME(bar)
BOOST_PARAMETER_NAME(baz)
BOOST_PARAMETER_NAME(bonk)

BOOST_PARAMETER_FUNCTION(
    (int),  // the return type of the function, the parentheses are required.
    function_with_named_parameters, // the name of the function.
    tag,  // part of the deep magic. If you use BOOST_PARAMETER_NAME you need to put "tag" here.
    (required // names and types of all required parameters, parentheses are required.
        (foo, (int))
        (bar, (float))
    )
    (optional // names, types, and default values of all optional parameters.
        (baz, (bool) , false)
        (bonk, (std::string), "default value")
    )
)
{
    if (baz && (bar > 1.0)) return foo;
    return bonk.size();
}


function_with_named_parameters(1, 10.0);
function_with_named_parameters(7, _bar = 3.14);
function_with_named_parameters( _bar = 0.0, _foo = 42);
function_with_named_parameters( _bar = 2.5, _bonk= "Hello", _foo = 9);
function_with_named_parameters(9, 2.5, true, "Hello");

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