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Questions tagged [default-arguments]

A default argument is a value passed to a certain parameter of a function if the user does not explicitly supply a value for that parameter.

A default argument is a value passed to a certain parameter of a function if the user does not explicitly supply a value for that parameter.

Some language extend this concept to other entities that have parameters. An example is C++, which has default template arguments, which is a value, type or template that is provided as an argument to a template parameter if the user does not explicitly provide an argument.

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Does PHP have "named parameters" so that early arguments can be omitted and later arguments can be written?

In PHP you can call a function with no arguments passed in so long as the arguments have default values like this: function test($t1 ='test1',$t2 ='test2',$t3 ='test3') { echo "$t1, $t2, $t3"; } test(); However, let's just say I want the last…
matthy
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How should Scala default arguments to refer to a previous positional argument?

Scala-lang reference 5.5.1 and 6.6.1 gave me the impression that a default parameter would be able to refer to a previously evaluated one: class Test(val first: String, val second: String = first) but from experimenting it seems the only way to do…
MilesHampson
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Why does using this C++ function twice in one line cause a compile error?

I ran into some trouble trying to implement a smart equality test macro-type template function in Visual C++ 2010 that had to do with a bug in VS in regard to default arguments of template functions. I fixed it by wrapping the value of the parameter…
neuviemeporte
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How to type mutable default arguments

The way to deal with mutable default arguments in Python is to set them to None. For example: def foo(bar=None): bar = [] if bar is None else bar return sorted(bar) If I type in the function definition, then the only type for bar says that…
Pro Q
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Clang does not notice default template parameters

Background According to the C++ standard, when forward-declaring a template type with default template parameters, each of them can appear in one declaration only. For example: // GOOD example template class Example; //…
andreasxp
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C++ default arguments in function overload evaluated once or each time?

I have a question on defaults for overload functions in an object. If I have a function signature as follows will the default value be evaluated only once or each time? class X { public: f(const RWDate& d=RWDate::now()); } // when calling f()…
bjackfly
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In C++, is a constructor with only default arguments a default constructor?

In the following code: struct Foo { Foo(int x=0); }; Does the constructor count as a default constructor?
Matt
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Provide default arguments for subscript operator and function call operator

In the following code, I have provided default arguments for array subscript operator. struct st { int operator[](int x = 0) { // code here } }; But, compiler generated an error : error: 'int st::operator[](int)' cannot have…
msc
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Dependent method types conflict with default arguments

When playing with scala's dependent method types, I encountered a conflict with default method parameters: abstract class X { type Y case class YY(y: Y) } object XX extends X { type Y = String } trait SomeTrait { def method(x: X)(y: x.YY,…
Alexander Bulaev
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Is it possible to use default arguments and a variable number of arguments in a single function?

For example, something like this: #include void my_function(int it=42, ...) { /* va_list/start/arg/end code here */ } What exactly does the above code mean in C++? It compiles fine in G++. Note, I can't imagine any scenario where…
Alessandro
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Verifying mocked object method calls with default arguments

Suppose I have this class: class Defaults { def doSomething(regular: String, default: Option[String] = None) = { println(s"Doing something: $regular, $default") } } I want to check that some other class invokes doSomething() method on…
Vladimir Matveev
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How to add void/null as default argument to a function/lambda pointer, in C++?

Present signature is template bool isPrime(const TypeData& n,TypeFunc fSqrt,bool debug = false) and this works perfectly with std::cout<<(isPrime(n,fSqrt)?"Positive":"Negative")<<'\n'; But, my intension is…
Supreeto
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How do I use overloaded functions with default arguments in algorithms?

I know the answer to the frequently-asked How do I specify a pointer to an overloaded function?: Either with assignment or with a cast, and every other C++ tutorial uppercases a string like this (give or take static_cast): transform(in.begin(),…
Cubbi
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Kotlin: how to make a function call using the first argument's default value and passing a value for the second?

I'd like to know how to call a function with default arguments when you want to specify the value of the second argument. In the simple example below I am showing that the addTwo() takes two arguments. The 'first' argument has a default value but…
hlupico
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Using rvalue references for default arguments

I want to make a function that takes an optional reference to an object, and creates one for the duration of the function if it is not provided, i.e. void Foo(Bar& b = Bar()) { /* stuff */ } This is, of course, invalid code, as a Bar cannot be…
Matt Kline
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