jerry gay jerrygaygmailcom wed aug 6 2008 858 yaakov belch wrote little language wrote time ago found useful let operator catch exceptions fx gy fx returns defined value use value fx returns undefined value use value gx instead fx throws exception catch keep use value gx dont catch exceptions gx similarly fx gy hz catches exceptions fx gy hz would like suggest semantics perl6 let explain useful think right thing first provides lightweight exception handling using wellknown ideoms like file_contentread_filefilename default_value compute_statisticsdata write_log_messagestats failed proposed change ideoms work whether functions throw exceptions right thing obviously fallback redundancy operator dont despair first computation doesnt produce usable result another way getting job done context exception conveys message undefined value first step failed need fall back alternative give second expression provides exactly alternative need jump normal processing order anymore dont think work perl 6 since perl 6 resumeable exceptions like c meaning c operator could ambiguous given following statement bill ack thpp ppt perl 6s current semantics c throws resumable exception handled current scope outer scope execution resume c definedness result c tested order determine whether call c using semantics resumable exception thrown c c cause c invoked immediately discarding possible defined result c also question arises c doesnt handle type exception thrown c called immediately c signify exception handled assign default value cbill mind strays far meaning c adds ambiguity makes operator unusable perhaps theres room operator gives sugar bill try ack catch thpp code concise enough doesnt warrant syntactic relief jerry wed 06 aug 2008 093616 0700 catching exceptions operator