In computer programming, a nullary constructor is a constructor that takes no arguments.[1] Also known as a 0-argument constructor, no-argument constructor,[2] parameterless constructor or default constructor.[3]
Object-oriented constructors
editIn object-oriented programming, a constructor is code that is run when an object is created. Default constructors of objects are usually nullary.[4]
Java example
editpublic class MyInteger {
private int data;
// Nullary constructor
public MyInteger() {
this(0);
}
// Non-nullary constructor
public MyInteger(int value) {
this.data = value;
}
int getData() {
return data;
}
void setData(int value) {
data = value;
}
}
C++ example
editclass Integer {
private:
int data;
public:
// Default constructor with parameters
// Leaving parameters unspecified defaults to the default value
Integer(int value = 0):
data{value} {}
[[nodiscard]]
int getData() const noexcept {
return data;
}
void setData(int value) noexcept {
data = value;
}
}
Algebraic data types
editIn algebraic data types, a constructor is one of many tags that wrap data. If a constructor does not take any data arguments, it is nullary.
Haskell example
edit-- nullary type constructor with two nullary data constructors
data Bool = False
| True
-- non-nullary type constructor with one non-nullary data constructor
data Point a = Point a a
-- non-nullary type constructor with...
data Maybe a = Nothing -- ...nullary data constructor
| Just a -- ...unary data constructor
See also
editReferences
edit- ^ "Default Constructor in Java – Class Constructor Example". freeCodeCamp.org. 2022-01-13. Retrieved 2022-03-23.
- ^ "No-argument Constructor". chortle.ccsu.edu. Retrieved 2022-03-23.
- ^ "Default constructors - cppreference.com". en.cppreference.com. Retrieved 2023-04-12.
- ^ Ottinger, Joseph B.; Linwood, Jeff; Minter, Dave (2022), Ottinger, Joseph B.; Linwood, Jeff; Minter, Dave (eds.), "An Introduction to Hibernate 6", Beginning Hibernate 6: Java Persistence from Beginner to Pro, Berkeley, CA: Apress, pp. 1–25, doi:10.1007/978-1-4842-7337-1_1, ISBN 978-1-4842-7337-1, retrieved 2022-03-23
{{citation}}: CS1 maint: work parameter with ISBN (link)
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