On Thu, Jul 26, 2012 at 9:58 AM, Adrian Mowat adrian.mo...@gmail.comwrote:
Hi Folks
I have a program that parses a string into rows and fields by repeatedly
applying a sequence of functions repeatedly until the end of the string is
reached. Each function (or chunker, as I have called them) knows how to
find the next field in the stream and returns the field and the remainder
of the input text.
I've come up with a recursive implementation as shown below but I am
wondering if this is idomatic or if there is a better way using while, for
or something like that?
(defn read-row [chunkers text]
Applies a list of functions to a string. Returns
a vector of fields found and any remaining text.
(read-row comma-chunkers \foo,bar,bop,baz,\) = [[\foo\ \bar\]
\bop,baz,\]
(reduce #(read-chunk %2 %1) (cons text chunkers)))
(defn read-all-rows [chunkers starting-text]
Repeatedly applies chunkers to text until the end of the
text is reached.
(reverse (loop [text starting-text result []]
Hi,
Reversing a list is common in Common Lisp to return a result in its proper
form.
In Clojure we usually use a vector data structure and the function `conj`
to do that.
It adds an item to a collection in the beginning or in the end depending of
the seq implementation (and in the case of a vector to the end, which is
what we what).
(if (empty? text)
result
(let [[row remainder] (read-row chunkers text)]
(recur remainder (cons row result)))
Always read seven times the Clojure core functions (http://clojuredocs.org,
and/or http://www.clojureatlas.com/) before using loop / recur: There's
probably a function in the core lib that do what you want.
In your particular case I am thinking of `take-while`.
(take-while even? [2 4 6 7 9])
(2 4 6)
My 2 cents.
Denis
The full source is at https://github.com/mowat27/clam
Hopefully that makes sense but please let me know if you have any queries
Many Thanks
Adrian
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