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

In rswipl: Embed 'SWI'-'Prolog'

class prolog_term {#class-prolog_term}

Class prolog_term is created by the XPCE/Prolog interface as a subclass of class host_data. It represents arbitrary Prolog terms, either as a handle to an term on the Prolog stack (term_t in SWI-Prolog, QP_term_ref in Quintus), or a reference to a term recorded in the Prolog database.

Instances of prolog_term are created using a direct reference to the prolog term. If the interface can no longer guarantee the lifefime of the term-reference, the interface checks whether the prolog_term object has references. If so, the term is recorded into the Prolog database, and the handle of the prolog_term object is changed to be a reference to the recorded term. If there are no references, the prolog_term object is simply discarded.

The XPCE type prolog is a disjunction of type prolog_term and type atomic (implying name, integer and real).

Send methods {#class-prolog_term-send}

• prolog_term->unlink If the prolog_term object refers to a term recorded into the Prolog database, ->unlink will remove it. This effectively leaves garbage collection of terms associated with XPCE data to XPCE.

Get methods {#class-prolog_term-get}

• prolog_term<-print_name: -> string Returns a string holding the term represented as text produced by write/1.

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