s-expression is a notation, with which nested lists can be represented in a textual form. In any lisp language, your code is not working with s-expressions, but with a data structure, which is most likely a cons.
s-expressions provide a convenient textual representation from which you can *read* or into which you can *print*. As Clojure offers more than one basic data structure for collections, it needs multiple notations in order to textually represent a collection type alongside its contents. While there is a cons type in Clojure, the clj syntax does not support traditional s-expression syntax for cons, e.g. (a . (b . NIL)). Closest you can get is with (a b), which creates a list. If your matcher does not need to differentiate between collection types, you can treat all collections as sequences and that way you can uniformly walk/transform any nested sequence. JW On Sun, Jan 19, 2014 at 6:40 PM, Dave Tenny <dave.te...@gmail.com> wrote: > As I try to reconcile my ancient past in writing common lisp code with a > clojure learning exercise, > I wonder whether clojure philosophy redefines the notion of an s-expression > or whether it just adds vectors and maps to s-expressions in without > trying to define what an s-expression is. > > The question came up as I was looking for a certain capability in clojure > libraries. > > Back in the day when lisps had only parenthesized collection types, there > were lisp libraries > (whose names I've long since forgotten) that would allow pattern matching > of s-expressions, > so that you could describe a pattern, match it to some tree, pick up > matches and continue to match some more. > > Sort of like java.util.Matcher.find(). > > However with every clojure program (and program output) being a huge set > of lists, vectors, and maps > I was looking for an s-exp matcher that would allow pattern expressions of > and matching against paths of combinations of these data structures. > > Sort of like enlive/select can traverse a nasty list/vector/map output of > enlive/html-resource with predicates that will match a sequence of nodes in > the web page. > (Only I don't think enlive/select returns matcher state that allows > continuation from where you left off, maybe it does, and of course it's > html oriented). > > Looking at the clojure.walk and clojure.zip stuff, I don't see anything > other than low level tools for certain kinds of traversals. > > What libraries are there for higher level "reach in and grab patterns of > data" abstractions that will work against a tree of lists/vectors/maps (and > preferably any other walkable data structure in clojure)? > > Looking for suggestions, and whatever philosophy there is about > s-expressions in clojure like reader environments. > > If I wanted lists, vectors, and maps with no zen, I'd be using python ;-) > > Thanks! > > -- > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to clojure@googlegroups.com > Note that posts from new members are moderated - please be patient with > your first post. > To unsubscribe from this group, send email to > clojure+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en > --- > You received this message because you are subscribed to the Google Groups > "Clojure" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to clojure+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. > -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
