Method or function?

[Rainer Deyke]

"Dale Strickland-Clark" <dale at out-think.NOSPAMco.uk> wrote in message
news:c3dtvs0uuleerbk6i44psnvmhqug6ghoec at 4ax.com...
> I dare say that this has been discussed before, I just can't see it
> anywhere.
>
> Shouldn't these standard functions be methods of their various
> datatype classes?

The number of methods of an object should be minimal, so that it is easier
to implement new classes/types with the same external interface.

> These are just the ones that seem obvious to me. There are a few more
> than I'm not sure about.
>
> abs

This one makes sense as a method, because there is no generic algorithm to
get the absolute value.  For example, calculating the absolute value of a
complex number requires a square root.

> chr

As a method of integer?  That would make the integer type dependent on the
string type, which is generally a bad idea.

> dir

The whole point of dir is that it can be applied to all objects (including
class instances) and it automatically works.

> eval

As a method of string?  Is there any advantage to this?  Methods in general
should be applicable to all instances of a type/class.

> execfile

See my comment of eval.

> filter

Filter applies to all sequences.  Do you want to write a new filter function
for each new sequence?

> float

This is a constructor function.

> hex

Suppose I want to write a function that converts an integer to a string in
base 5.  I could call it quint.  Now, would it make any sense for hex to be
a method while quint is an external function?  Or should I modify the Python
core to also make quint a method?

> id

id applies to all objects, including methods.  Do you really want
1.id().id().id() to be legal Python?

> int

Constructor function.

> len

This makes sense as a method, somewhat.

> list

Constructor function.  If a write a new sequence class called "linked_list",
should I modify all existing sequence types to have a linked_list method?

> long

Constructor.

> map

As method of what?  The function?  The sequence?  Which one?

> max
> min

1.max(2) # Evaluates to 2
1.min(2) # Evalutes to 1

I rest my case.

> oct

See hex.

> ord

This would make sense as a method, somewhat.

> pow

This is just a shortcut for the power operator (a ** b).  The power operator
is overloaded like any other operator (__pow__ for class instances).

> reduce

See: map

> repr

Applies to all objects.  repr has a default behavior for class instances,
which can be modified by defining __repr__.  If this was a method, there
could be no default behavior.

> round

This might make sense as a method.

> str

See: repr

> tuple

Constructor.

> unichr

Do you really want to change the external interface of integers just because
we have a new string type?

> vars

See: dir


--
Rainer Deyke (root at rainerdeyke.com)
Shareware computer games           -           http://rainerdeyke.com
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