Thanks David.
On Mar 9, 4:22 pm, David Nolen <[email protected]> wrote:
> The first regex is returning an empty list not nil.
> David
>
> On Mon, Mar 9, 2009 at 11:48 AM, timc <[email protected]> wrote:
>
> > Can someone please see what's wrong with this.
>
> > (defn getArg [arg]
> > "Return a [keyword value] depending on the form of the string arg:
> > 1. arg is of the form +x ==> [:x true].
> > 2. arg is of the form -x ==> [:x false].
> > 3. arg is of the form x=v ==> [:x v].
> > 4. else ==> [:files arg]."
> > (let [x (or
> > (re-seq #"([+])([a-zA-Z_0-9]+)" arg)
> > (re-seq #"([-])([a-zA-Z_0-9]+)" arg)
> > (re-seq #"([a-zA-Z_0-9]+)=([^ ]+)" arg))]
> > (if (nil? x) [:files arg]
> > (let [x (first x)
> > y (nth x 1)
> > z (nth x 2)]
> > (cond
> > (= y "+") [(keyword z) true]
> > (= y "-") [(keyword z) false]
> > :else [(keyword y) z])))))
>
> > This is part of a command-line-arg processing function. I want to end
> > up with a map containing things like this:
>
> > {:verbose true :fast false :configFile "/tom/dick" :files ["foo" "bar"
> > "zot"]}
>
> > as a result of processing the command line args:
>
> > +verbose -fast configFile=/tom/dick foo bar zot
>
> > Now...
>
> > (getArg "+foo") correctly returns [:foo true]
>
> > however
>
> > (getArg "-foo") throws a NullPointerException.
>
> > Am I wrong in my understanding of the or function? That is, that (or a
> > b c) should return the first of a,b,c that returns true (i.e. non-nil)
> > or nil if they are all nil?
>
> > Or is something happening to the function 'arg' inside the let?
>
> > Thanks in advance.
>
> > ---------------------------------------
> > In case it's interesting to anyone, the other part of this (that calls
> > getArg) is the following.
>
> > (defn getArgs [args & xs]
> > "This processes args (a seq of strings) and returns a map.
> > The parameter xs is a seq of two-element vectors: [keyword value].
> > The returned map contains (keyword,value) pairs produced by
> > processing the args, as follows.
> > 1. An arg of the form +x creates the pair (:x true).
> > 2. An arg of the form -x creates the pair (:x false).
> > 3. An arg of the form x=v creates the pair (:x v), where v is a
> > string.
> > 4. Any other args will be placed in the pair (:files
> > vectorOfStrings).
> > 5. Any [x v] in xs, not found in the args, will create the pair (:x
> > v)."
> > (let [res {:files []}]
> > ; First process the args (if any).
> > (when args (doall (for [arg args]
> > (let [ga (getArg arg) [key val] ga]
> > (cond
> > (= key :files) (conj (:files res)
> > val)
> > :else (conj res ga))))))
> > ; Now process the xs (if any).
> > (when xs (doall (for [x xs]
> > (let [key (first x)]
> > (when (not (key res)) (conj res x))))))
> > res))
>
> > so that (for example)
>
> > (def cmdArgs (getArgs *command-line-args* [[:verbose false] [:fast
> > true] [:configFile "/tom/harry"] [:something "someValue"]]))
>
> > both gets command line params into the map cmdArgs and/or creates
> > entries with default values. What is does NOT do is validate the
> > parameters.
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