[#util-Expected-0b]
= xref:util.adoc[util]::Expected
:relfileprefix: ../
:mrdocs:

The util::Expected class provides a standard way for low‐level functions to return either error values or result values.

== Synopsis

Declared in `<util/expected.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class T,
    class E>
class Expected;
----

== Description

It provides a smaller version of std::expected from C++23. Missing features can be added, if needed.

== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:util/Expected-0b/2constructor-05.adoc[`Expected`]         [.small]#[constructor]#
| Constructors
| xref:util/Expected-0b/error-0af.adoc[`error`] 
| Access the stored error (undefined behavior if a value is held).
| xref:util/Expected-0b/has_value.adoc[`has_value`] 
| Test whether a result value is held.
| xref:util/Expected-0b/operator_star-04.adoc[`operator*`] 
| Access the result value without checking.
| xref:util/Expected-0b/operator_ptr-046.adoc[`operator‐>`] 
| Access members of the result value.
| xref:util/Expected-0b/swap.adoc[`swap`] 
| Swap contents with another Expected.
| xref:util/Expected-0b/value-05.adoc[`value`] 
| Access the result value, throwing if an error is held.
| xref:util/Expected-0b/value_or-0c.adoc[`value_or`] 
| Return the result value, or a fallback when an error is held.
| xref:util/Expected-0b/2conversion.adoc[`operator bool`] 
| Test whether a result value is held.
|===


== Specializations

[cols="1"]
|===
| Name
| xref:util/Expected-05.adoc[`Expected<void, E>`] 
|===


== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:FeeRateEstimationRef.adoc[`::FeeRateEstimationRef`]
| Return the estimation carried by a fee rate estimate result: the successful estimation, or the error's zero‐value estimation.
| xref:ParseKeyPathElement.adoc[`::ParseKeyPathElement`]
| Parse a single key path element like "0", "0'", or "0h". Returns the derivation index and hardened status, or an error message.
| xref:SignPSBTInput.adoc[`::SignPSBTInput`]
| Signs a PSBTInput, verifying that all provided data matches what is being signed.
| xref:wallet/ExportDescriptors.adoc[`::wallet::ExportDescriptors`]
| Export the descriptors from a wallet so that they can be imported elsewhere
|===


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