# Default Constructible

Category: utilities | Component type: concept

### Description

A type is DefaultConstructible if it has a default constructor, that is, if it is possible to construct an object of that type without initializing the object to any particular value.

### Refinement of

### Associated types

### Notation

`X` | A type that is a model of DefaultConstructible
`x` | An object of type `X`

### Definitions

### Valid expressions

Name | Expression | Type requirements | Return type
--- | --- | --- | ---
Default constructor | `X()` |  | `X`
Default constructor | `X x;` [1] |  |

### Expression semantics

Name | Expression | Precondition | Semantics | Postcondition
--- | --- | --- | --- | ---
Default constructor | `X()` |  |  |
Default constructor | `X x;` |  |  |

### Complexity guarantees

### Models

- int
- `vector<double>`

### Notes

[1] The form `X x = X()` is not guaranteed to be a valid expression, because it uses a copy constructor. A type that is DefaultConstructible is not necessarily Assignable

### See also

Assignable

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