On Oct 16, 4:29 pm, Rich Hickey <[EMAIL PROTECTED]> wrote:
> On Oct 15, 11:47 pm, "Stephen C. Gilardi" <[EMAIL PROTECTED]> wrote:
>
>
>
> > Hi Parth,
>
> > > But if I do this in a doto, it doesn't seem to work but
> > > I don't get any error message.
>
> > > user=> (doto (new java.lang.String "hello") (toUpperCase))
> > > "hello"
> > > user=> (class (new java.lang.String))
> > > #=java.lang.String
>
> > > Shouldn't this be working? If this is (by design) because strings are
> > > immutable (so no doto) shouldn't there be an error message?
>
> > > What am I missing here.
>
> > "doto" operates on an object and returns the object that it operated
> > on. In your case, it's the original string that gets returned. Strings
> > are immutable so the toUpperCase call created a new string which was
> > then thrown away.
>
> > The "->" operator will accomplish what you're looking for here. It
> > returns the result of the operations, each result becoming the input
> > for the next::
>
> > user=> (-> (String. "hello") .toUpperCase)
> > "HELLO"
>
> Another semantic marker here is 'do'. do in Clojure implies side-
> effects. Since you can't uppercase a string by side effect, doto isn't
> the right tool for this job.
>
> doto can't throw an error here or elsewhere when used on an immutable
> object because:
>
> a) It can't generally know which objects are immutable
> b) Even immutable objects may have methods with other side-effects
>
> Rich
That makes sense. Thanks everyone for all the help.
Parth
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