PEP Proposal

[python-pep at arcor.de]

Hi,

sorry, I have these ideas for longer than 10 years, please have a look on it
and comment on it. Thx.


----

This is another proposal for introducing types into Python.

There are many reasons for incorporating types into Python, but there is
also a lot of concern about doing so because of destroying the original
character of Python as a smart script language.

This proposal adds several advantages of Prolog(ue) techniques without
changing the natural understanding of Python as a language.


Proposal:

1. Method definitions can be non-unique if a type is prefixed to one or more
of its parameters, or the parameters differ in number.

2. A keyword 'reject' is added.

3. A keyword 'fail' is added.

4. A keyword 'cut' is added.


Definition:

1. A "type" is a String naming the actual class or class family which the
passed instanced is derived from, prefixing the parameter.

2. "'reject'" is a marker inside a function/method and signals that further
processing will not be done inside this method, but instead be passed to the
next available function/method in row, otherwise an implicit "fail" will
occur.

3. "'fail'" is a marker inside a function/method and signals that NO further
processing can be done in neither of this or the following
functions/methods.

4. "'cut'" is a marker inside a function/method that signals that the
failure of called functions/methods inside of it, following this statement,
automatically lead to a failure, instead of trying the next method -
normally, it would be "reject" instead.

5. Failure of functions/methods to outside of this new context are signalled
with a new exception e.g. "MethodRetrialError".



E.g.

def whoisthethief("List" x):
  return iknowit(x)

def whoisthethief("String" x, "String" y):
  return iknowit([x,y])

##########

def numeral_add(a, b):
  if type(a)!=types.IntType:
    reject
  ...

# equivalent to:

def numeral_add("Integer" a, b):
  ...