PEP Proposal

Aaron "Castironpi" Brady castironpi at gmail.com
Fri Sep 26 03:01:22 CEST 2008


On Sep 25, 2:24 pm, python-... at arcor.de wrote:
> 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):
>   ...

Would you settle for a class or classes which had the same
functionality, only you would call its methods with parentheses?

Modified examples:

@argtype( List )
def whoisthethief(x):
  return iknowit(x)

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

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

/or:

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



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