Subject: Re: Testing if an attribute is present From: Paul Prescod <papresco@xxxxxxxxxxxxxxxx> Date: Mon, 27 Oct 1997 12:58:06 -0500 |
Vivek Agrawala wrote: > Here is a procedure that illustrates how to check for an attribute: > > (define (get-str-attr-no-err attr-nm snl) > (let ((a-str (attribute-string attr-nm snl))) > (if (equal? a-str #f) "" a-str) )) > > To use it: > (get-str-attr-no-err "DAY" (current-node)) A nice idiom I've seen would be a good extension to your function: (define (get-str-attr-no-err attr-nm #!optional (osnl (current-node)) #!key (default "") ) (let ((a-str (attribute-string attr-nm osnl))) (if (equal? a-str #f) key a-str) )) Then you can call the function like this: (get-str-attr-no-err "DAY" default: "Sunday" ) But first you'll have to fix the typos in my untested code above. :) Paul Prescod DSSSList info and archive: http://www.mulberrytech.com/dsssl/dssslist
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