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====== Function SLOT-BOUNDP ====== ====Syntax==== * **slot-boundp** //instance slot-name// → //generalized-boolean// ====Arguments and Values==== * //instance// - an //[[CL:Glossary:object]]//. * //slot-name// - a //[[CL:Glossary:symbol]]// naming a //[[CL:Glossary:slot]]// of //instance//. * //generalized-boolean// - a //[[CL:Glossary:generalized boolean]]//. ====Description==== Returns //[[CL:Glossary:true]]// if the //[[CL:Glossary:slot]]// named //slot-name// in //instance// is bound; otherwise, returns //[[CL:Glossary:false]]//. ====Examples==== None. ====Affected By==== None. ====Exceptional Situations==== If no //[[CL:Glossary:slot]]// of the //[[CL:Glossary:name]]// //slot-name// exists in the //instance//, **[[CL:Functions:slot-missing]]** is called as follows: <blockquote> ([[CL:Functions:slot-missing]] ([[CL:Functions:class-of]] //instance//) //instance// //slot-name// 'slot-boundp) </blockquote> (If **[[CL:Functions:slot-missing]]** is invoked and returns a value, a //[[CL:Glossary:boolean equivalent]]// to its //[[CL:Glossary:primary value]]// is returned by **slot-boundp**.) The specific behavior depends on //instance//'s //[[CL:Glossary:metaclass]]//. An error is never signaled if //instance// has //[[CL:Glossary:metaclass]]// **[[CL:Types:standard-class]]**. An error is always signaled if //instance// has //[[CL:Glossary:metaclass]]// **[[CL:Types:built-in-class]]**. The consequences are undefined if //instance// has any other //[[CL:Glossary:metaclass]]// - an error might or might not be signaled in this situation. Note in particular that the behavior for //[[CL:Glossary:conditions]]// and //[[CL:Glossary:structures]]// is not specified. ====See Also==== * **[[CL:Functions:slot-makunbound|Function SLOT-MAKUNBOUND]]** * **[[CL:Functions:slot-missing|Generic Function SLOT-MISSING]]** ====Notes==== The //[[CL:Glossary:function]]// **slot-boundp** allows for writing //[[CL:Glossary:after methods]]// on **[[CL:Functions:initialize-instance]]** in order to initialize only those //[[CL:Glossary:slot|slots]]// that have not already been bound. Although no //[[CL:Glossary:implementation]]// is required to do so, implementors are strongly encouraged to implement the //[[CL:Glossary:function]]// **slot-boundp** using the //[[CL:Glossary:function]]// **[[CL:Functions:slot-boundp-using-class]]** described in the //[[CL:Glossary:Metaobject Protocol]]//. \issue{SLOT-MISSING-VALUES:SPECIFY} \issue{SLOT-VALUE-METACLASSES:LESS-MINIMAL}