I need a simple utility that will return the numeric value represented by a string y, following the rules of dyadic ". except returning the scalar x if y is empty. This should be fast since it is to be applied under > to large arrays of boxed strings whose exact format cannot be controlled. I have observed that if y is preceded by a TAB the result of ". is unchanged, and if y is a TAB alone the result is x; therefore adding a TAB before (each) y seems to do the trick. But this is not documented in the Vocabulary. Can I trust this behaviour to continue in future editions of J?
Adding a space would seem more natural but ". treats y that is all spaces like an empty vector. Best would be if the left argument to ". had an optional second element, specifying the exact number of elements to be returned in each row, or default 0 for the present behaviour. Then I could force an empty y to receive the padding value 0{x. Thanks, Richard Vaughan This message is intended only for the addressee and may contain information that is confidential or privileged. Unauthorized use is strictly prohibited and may be unlawful. If you are not the intended recipient, or the person responsible for delivering to the intended recipient, you should not read, copy, disclose or otherwise use this message, except for the purpose of delivery to the addressee. If you have received this email in error, please delete and advise the IT Security department at info...@thewg.com immediately. Please consider the environment before printing this e-mail. ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm