Re: constructors with mix of params and Map

> Quoting Alexandru Popescu ☀ <the.mindstorm.mailinglist@...>:
>
> > On 10/9/07, Guillaume Laforge <glaforge@...> wrote:
> >> Is there some reason (use case?) which triggered this idea?
> >> Frankly, I'm not too fond of mixing maps and parameters too much.
> >>
> >
> > Python supports the following format:
> >
> > positional arguments
> > *args:
> > **args: named parameters
> >
> > This seems to work oke there. But I don't think that mixing them makes sense.
>

> You can't mix them in Python, either. The order must be:
>
> - Normal parameters
> - Keyword arguments (or arguments with default value).
> - Argument lists
> - Maps
>
> In the code, this looks like so:
>
> def f(arg, argWithDefault='default value', *args, **kw):
>      print 'arg=%s, argWithDefault=%s, *args=%s, **kw=%s' % (str(arg),
> str(argWithDefault), str(args), str(kw))
>
> Resolution:
>
> - The first parameter is stored in "arg"
> - If there is a second parameter, then the value is stored in
> "argWithDefault". If there isn't, "argWithDefault" has the value
> 'default value'. Note: The value is evaluated once. If you say, for
> example, x=[] to define a list, all invocations of f() will be passed
> the same list instance.
> - All other, unnamed arguments end up in *args which is a list
> - All named arguments end up in the map **kw.
>
> Examples:
>
> f() -> Error, because arg is missing
> f(1) -> arg=1, argWithDefault='default value', *args=[], **kw={}
> f(1,2) -> arg=1, argWithDefault=2, *args=[], **kw={}
> f(1,2,3) -> arg=1, argWithDefault=2, *args=[3], **kw={}
> f(1,2,3,4) -> arg=1, argWithDefault=2, *args=[3,4], **kw={}
> f(1,2,3,4, argWithDefault=5) -> Error: Value of argWithDefault is
> specified twice.
> f(1,argWithDefault=5,2,3,4) -> Error: non-keyword arg after keyword arg
> f(1,2,3,4,a=5) -> arg=1, argWithDefault=2, *args=(3, 4), **kw={'a': 5}
>
> > ./alex
> > --
> > .w( the_mindstorm )p.
> >
> >> On 10/9/07, Alex Tkachman <alex.tkachman@...> wrote:
> >> > Do we want to code like this where constructor params mixed with named
> >> > properties?
> >> >
> >> > class Book {
> >> >   Book (String author, String coauthor) {
> >> >       this.author = author
> >> >       this.coauthor = coauthor
> >> >   }
> >> >
> >> >   String title, author, coauthor
> >> > }
> >> >
> >> > class SuperBook extends Book {
> >> >   SuperBook (Map map, String author, String coauthor) {
> >> >       super (author, coauthor)
> >> >       title = "SuperBook"
> >> >   }
> >> > }
> >> >
> >> > class NewInstanceTest extends GroovyTestCase{
> >> >     void testNewInstance () {
> >> >        def book = Book.newInstance("Alex", title: "All about it",
> >>  "Graeme" )
> >> >        assertEquals book.title, "All about it"
> >> >        assertEquals book.author, "Alex"
> >> >        assertEquals book.coauthor, "Graeme"
> >> >     }
> >> >
> >> >     void testConstructor () {
> >> >        def book = new Book("Alex", title: "All about it", "Graeme" )
> >> >        assertEquals book.title, "All about it"
> >> >        assertEquals book.author, "Alex"
> >> >        assertEquals book.coauthor, "Graeme"
> >> >     }
> >> >
> >> >     void testSuper () {
> >> >        def book = new SuperBook("Alex", title: "All about it", "Graeme" )
> >> >        assertEquals book.title, "SuperBook"
> >> >        assertEquals book.author, "Alex"
> >> >        assertEquals book.coauthor, "Graeme"
> >> >     }
> >> > }
> >> >
> >> > ---------------------------------------------------------------------
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> >> >
> >> >
> >>
> >>
> >> --
> >> Guillaume Laforge
> >> Groovy Project Manager
> >> http://glaforge.free.fr/blog/groovy
> >>
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> >>
> >>
> >
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> >
> >
> >
>
>
>
> --
> Aaron "Optimizer" Digulla a.k.a. Philmann Dark
> "It's not the universe that's limited, it's our imagination.
> Follow me and I'll show you something beyond the limits."
> http://www.pdark.de/
>
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