CODEWITHSUNDEEP
c++
user2756669
user2756669

Reputation: 123

Functions and arguments

If I have a function such as 

int mathscalc (int a, int b = 5)
{

}

And I call the function mathscalc(a), how can I only do 1 argument when it requires 2? if that's possible.

Upvotes: 0

Views: 132

Answers (6)

User25
User25

Reputation: 15

Yes, those function calls are possible and are known as default arguments. The default arguments should be used in the last, the inverse of that ie.,

int mathscalc (int a = 5, int b)

is not possible.

If the corresponding function call is made as,

mathscalc (5,6); 'b' will take value 6,

else if it is made as mathscalc (5); 'b' will take the default value 5.

Upvotes: 0

Saravanan
Saravanan

Reputation: 1440

If you make call to mathscalc function with one say,

   mathscalc(4);

Compiler intern changes this function with 

   mathscalc(4, 5);

But, if you make a call with two args say,

   mathscalc(4, 10);

Compiler will not replace that b with 5 instead it uses 10 in the place of b.

Upvotes: 0

weiglt
weiglt

Reputation: 1079

b has a default value. If it is not specified, it is 5, if it is specified, it is the value, that is given.

For example:

mathscalc(3, 10) // b is 10 inside the function call

mathscalc(3) // b is 5 inside the function call

Upvotes: 5

billz
billz

Reputation: 45470

This is well explained in C++11 Standard.

§8.3.6 Default arguments [dcl.fct.default]

1 If an initializer-clause is specified in a parameter-declaration this initializer-clause is used as a default argument. Default arguments will be used in calls where trailing arguments are missing.

2 [ Example: the declaration

void point(int = 3, int = 4);

declares a function that can be called with zero, one, or two arguments of type int. It can be called in any of these ways:

point(1,2); point(1); point();

The last two calls are equivalent to point(1,4) and point(3,4), respectively. —end example ]

3 A default argument shall be specified only in the parameter-declaration-clause of a function declaration or in a template-parameter (14.1); in the latter case, the initializer-clause shall be an assignment-expression. A default argument shall not be specified for a parameter pack. If it is specified in a parameter-declarationclause, it shall not occur within a declarator or abstract-declarator of a p*arameter-declaration*.

Upvotes: 1

Shankar Narayana Damodaran
Shankar Narayana Damodaran

Reputation: 68556

A value of 5 has been already assigned to the variable b in your mathscalc function.

So if you pass value 2 to a , say the mathscalc has a multiplication operation of c = a*b; the result of c will be 10.

If you explicitly pass a=2 and b=3 to your mathscalc function, the existing value assigned to b=5 will be overwritten to b=3, so the result of c will be 6.

Upvotes: 0

Paul Evans
Paul Evans

Reputation: 27577

If you call mathscalc with only one argument then b will be set to it's default 5.

Upvotes: 0

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