2016-11-21 8:34 GMT+01:00 Jan Synáček <jan.syna...@gmail.com>: > > Ok. Apart from the fact that it's written in srfi, I wonder what the > reasoning for such behavior is. I mean, what makes the "i" bigger than > the length of the list so illegal that you have to bail out? When is > such behavior useful? On the other hand, not having to worry about the > list length is very useful. Because now my code is littered with > things like > > ;; Let's hope that string-length is O(1). > (if (>= width (string-length item)) > item > (string-take item width)) > > or > > (if (string-null? text) > "" > (string-drop-right text 1)) > > Maybe I'm just doing something wrong? >
The variants of take and drop that you'd like to have would need to perform additional checks in order to find out whether the object that you are trying to drop or take is a pair. When it comes to your code, it's really hard to say if you're doing something wrong or not, because it doesn't say why you're doing what you're doing. But in the case of string operations it is often more convenient to use regular expressions. (However, I admit that I rarely have the need to use take-upto and drop-upto functions. I ofen use the split-at function, and I really appreciate that it throws an error when invoked with an index that lies beyond a given list; otherwise, I'd have to worry about silent errors that could appear in my code. Likewise, you could have (car '()) and (cdr '()) return an empty list, which would make your code "fool proof", but I don't think it would have good implications in the long run. Anyway, even Haskell's head and tail don't work like that)
