src/swipl-devel/packages/xpce/man/refmanual/md/binding.md

In rswipl: Embed 'SWI'-'Prolog'

class binding {#class-binding}

Name/Value pair used to pass named arguments to methods. A binding is written as Name := Value and is recognised by send_method ->send when it scans an argument list, allowing the caller to skip optional arguments by name. See send_method ->send for the full argument binding rules.

The following example creates a menu_item named help whose end_group slot is set via a binding rather than by positional arguments:

?- new(X, menu_item(help, end_group := @on)).

@see send_method->send

Instance variables {#class-binding-instvars}

• binding<->name: name Name of the formal argument or slot to bind.

• binding<->value: any|function Value to bind it to. If a function is supplied it is evaluated before assignment.

Send methods {#class-binding-send}

• binding->initialise: name=name, value=any|function Create a binding from a name and a value. Normally written using the := syntactic shorthand rather than constructed explicitly.

rswipl documentation built on June 16, 2026, 5:07 p.m.