Types

The Nextflow standard library defines the types that are available in a pipeline. You can use these types to annotate pipeline parameters, process inputs and outputs, and workflow inputs and outputs. See Static typing for an overview.

Primitive types

Page	Description
Boolean	true or false.
Float	A floating-point number.
Integer	A whole number.
String	An immutable sequence of characters.

Collection types

Page	Description
Bag<E>	An unordered collection of values.
Iterable<E>	The trait implemented by collection types that support iteration.
List<E>	An ordered collection of values.
Set<E>	An unordered collection of unique values.

Composite types

Page	Description
Map<K,V>	A mapping of key-value pairs.
Record	An immutable map of fields to values, where each value can have its own type.
Tuple	A fixed sequence of values, where each value can have its own type.

Dataflow types

Page	Description
Channel<E>	An asynchronous sequence of values.
Value<V>	An asynchronous value.

Other types

Page	Description
Duration	A duration of time.
MemoryUnit	A quantity of bytes.
Path	A handle for files, directories, and URLs.
VersionNumber	A semantic or calendar version number.

See also

• Namespaces: The constants and functions that return these types.
• Semantics: How Nextflow evaluates values and expressions that use these types.