Hi all,
There is an omission in the core clojure library: there is no way to
create a file reader.
I follow the scheme of regex: all the verbosity of java.util.regex.*
classes is hidden away, in a beautiful set of small (and heavily used)
functions.
For file I/O, though, core clojure has functions that deal with readers,
like for example line-seq, but there is not a single function to create
a reader trivially.
Currently, one must resort to incantations like:
(with-open [stream (java.io.BufferedReader.
(java.io.FileReader.
"/home/albert/test.xml"))]
(doseq [line (line-seq stream)]
(println line)))
... which require writing in imports or fully qualified names for
java classes whose existence I wish I could forget about.
In order to use clojure from a REPL, just like I'd use Matlab or R or
similar programs, a file-reader generator is missing. Every clojure
user is going to have to reinvent the wheel, in the form of custom
code in the user.clj to avoid excessive and avoidable typing.
I understand one of the main problems is the required ".close" call on
the reader, which so far is taken care of by the macro with-open.
So: why not have a file-reader function in core clojure, that MUST
be invoked from within a with-open macro (or throws an exception)?
This would be the same scheme of dosync and alter/commute/etc.
Then we'd write:
(with-open [rdr (file-reader "/home/albert/test.xml")]
(doseq [line (line-seq stream)]
(println line)))
The above would only be necssary when lazyness is a requirement. So,
even better, in the spirit of the do-it-all "slurp" function, how about
a non-lazy (hence no ".close" call issue) slurp-lines function?
(Sure, one can write (vec (.split (slurp "/home/albert/test.xml") "\n"))
but that
again implies one knows the java API by heart.)
Adding the above 2 functions and moving spit from clojure-contrib into core
would finally make the clojure REPL a great REPL for text data I/O, and
thus for data analysis in a research lab.
Albert
--
Albert Cardona
http://albert.rierol.net
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