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								< head >  
						 
					
						
							
								
									
										
										
										
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									< meta  http-equiv = "content-type"  content = "text/html; charset=iso-8859-1"  / > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
									< title > Logtalk built-in method: retract/1< / title > 
							 
						 
					
						
							
								
									
										
										
										
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									< link  rel = "stylesheet"  href = "../../screen.css"  type = "text/css"  media = "screen" / > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
									< link  rel = "stylesheet"  href = "../../print.css"  type = "text/css"  media = "print" / > 
							 
						 
					
						
							
								
									
										
										
										
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								< div  class = "top-left" > Logtalk reference manual< / div >   
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								< div  class = "top-right" > Built-in method: retract/1< / div >  
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								< div  class = "bottom-left" > < span  class = "page" / > < / div >   
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
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								< div  class = "navtop" > < a  href = "../../index.html" > contents< / a >  >  < a  href = "../index.html" > reference manual< / a >  >  < a  href = "../index.html#methods" > built-in methods< / a > < / div >  
						 
					
						
							
								
									
										
										
										
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								< h2  class = "code" > retract/1< / h2 >  
						 
					
						
							
								
									
										
										
										
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								< h4 > Description< / h4 >  
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
									
										
										
										
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								< pre > retract(Clause) 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								retract((Head:-Body))< / pre > 
							 
						 
					
						
							
								
									
										
										
										
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								< p >  
						 
					
						
							
								
									
										
										
										
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									Retracts a dynamic clause from an object.
							 
						 
					
						
							
								
									
										
										
										
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								< / p >  
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								< h4 > Template and modes< / h4 >  
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
									
										
										
										
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								< pre > retract(+clause)< / pre >  
						 
					
						
							
								
									
										
										
										
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								< h4 > Errors< / h4 >  
						 
					
						
							
								
									
										
										
										
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								< dl  class = "errors" >  
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
									< dt > Head is a variable:< / dt > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
										< dd > < code > instantiation_error< / code > < / dd > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
									< dt > Head is neither a variable nor a callable term:< / dt > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
										< dd > < code > type_error(callable, Head)< / code > < / dd > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
									< dt > The predicate indicator of Head is that of a private predicate:< / dt > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
										< dd > < code > permission_error(modify, private_predicate, Head)< / code > < / dd > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
									< dt > The predicate indicator of Head is that of a protected predicate:< / dt > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
										< dd > < code > permission_error(modify, protected_predicate, Head)< / code > < / dd > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
									< dt > The predicate indicator of Head is that of a static predicate:< / dt > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
										< dd > < code > permission_error(modify, static_predicate, Head)< / code > < / dd > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
									< dt > The predicate indicator of Head is not declared:< / dt > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
										< dd > < code > existence_error(predicate_declaration, Head)< / code > < / dd > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								< / dl >  
						 
					
						
							
								
									
										
										
										
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								< h4 > Examples< / h4 >  
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								
							 
						 
					
						
							
								
									
										
										
										
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								< dl  class = "examples" >  
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
									< dt > To retract a matching clause of any dynamic predicate in < a  class = "glossary"  title = "Go to glossary definition"  href = "../../glossary.html#this" > this< / a > :< / dt > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
										< dd > < code > retract(Clause)< / code > < / dd > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
									< dt > To retract a matching clause of a public or protected dynamic predicate in < a  class = "glossary"  title = "Go to glossary definition"  href = "../../glossary.html#self" > self< / a > :< / dt > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
										< dd > < code > ::retract(Clause)< / code > < / dd > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
									< dt > To retract a matching clause of a public dynamic predicate in an object:< / dt > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
										< dd > < code > Object::retract(Clause)< / code > < / dd > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
								< / dl >  
						 
					
						
							
								
									
										
										
										
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									< div  class = "navbottom" > < a  href = "clause2.html" > previous< / a >  | < a  href = "../../glossary.html" > glossary< / a >  | < a  href = "retractall1.html" > next< / a > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
									< div  class = "copyright" > Copyright ©  < a  href = "mailto:pmoura@logtalk.org" > Paulo Moura< / a >  —  < a  href = "http://www.logtalk.org" > Logtalk.org< / a > < / div > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
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										< span  class = "date" > Last updated on: November 16, 2005< / span > 
							 
						 
					
						
							
								
							 
							
								
							 
							
								 
							
							
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								< / body >  
						 
					
						
							
								
									
										
										
										
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