Re: Overloading the tilde operator?
[EMAIL PROTECTED] writes: > Also some flavours of Prolog, as descrived in the classic book by op/3 is part of the Prolog ISO standard: http://pauillac.inria.fr/~deransar/prolog/bips.html#operators so every compliant implementation has it. -- http://mail.python.org/mailman/listinfo/python-list
Re: Overloading the tilde operator?
On Feb 8, 7:02 am, Dave Benjamin <[EMAIL PROTECTED]> wrote: > Neil Cerutti wrote: > > There's been only one (or two?) languages in history that > > attempted to provide programmers with the ability to implement > > new infix operators, including defining precedence level and > > associativity (I can't think of the name right now). > > You're probably thinking of SML or Haskell. OCaml also allows you to > define new infix operators, but the associativities are fixed (and > determined by what punctuation you use). Also some flavours of Prolog, as descrived in the classic book by Clocksin & Mellish. Regarding the OP, I hope his need for an infix tilde operator is overestimated; there are plenty of infix operators that can be abused, and at least one of them should be unused and available for redefinition. Lorenzo Gatti -- http://mail.python.org/mailman/listinfo/python-list
Re: Overloading the tilde operator?
Dave Benjamin wrote: > Neil Cerutti wrote: > >> There's been only one (or two?) languages in history that >> attempted to provide programmers with the ability to implement >> new infix operators, including defining precedence level and >> associativity (I can't think of the name right now). > > You're probably thinking of SML or Haskell. OCaml also allows you to > define new infix operators, but the associativities are fixed (and > determined by what punctuation you use). Prolog lets you do this, too. In Smalltalk, you can use just about any sequence of non-letters as an infix operator, but it has no notion of precedence, even for the built-in operators. I think SNOBOL may have had something for defining new operators, but I can't remember the details. -- Greg -- http://mail.python.org/mailman/listinfo/python-list
Re: Overloading the tilde operator?
Neil Cerutti wrote: > There's been only one (or two?) languages in history that > attempted to provide programmers with the ability to implement > new infix operators, including defining precedence level and > associativity (I can't think of the name right now). You're probably thinking of SML or Haskell. OCaml also allows you to define new infix operators, but the associativities are fixed (and determined by what punctuation you use). -- http://mail.python.org/mailman/listinfo/python-list
Re: Overloading the tilde operator?
James Stroud wrote: > You haven't addressed why the limitation isn't arbitrary. It's not arbitrary because there is a built-in meaning for infix minus, but not for infix tilde. Python doesn't go out of its way to provide operators which aren't used by at least one built-in type. -- Greg -- http://mail.python.org/mailman/listinfo/python-list
Re: Overloading the tilde operator?
On 2007-02-02, Ben Finney <[EMAIL PROTECTED]> wrote: > James Stroud <[EMAIL PROTECTED]> writes: >> Ben Finney wrote: >> > The Python runtime parser is designed to parse Python, not >> > some arbitrary language that someone chooses to implement in >> > Python. >> >> You haven't addressed why the limitation isn't arbitrary. > > Good thing I wasn't trying to do that, then. I was pointing out > the source of the limitation. > > The Python syntax parser must follow the rules of the Python > language. If you accept that premise, it follows that the '~' > operator is unary only. If you *don't* accept that premise, I > have no help to offer. There's been only one (or two?) languages in history that attempted to provide programmers with the ability to implement new infix operators, including defining precedence level and associativity (I can't think of the name right now). C++, for example, works the same way as Python here. You can override most of the operators, but you cannot change their arity, associativity, or precedence level. -- Neil Cerutti Let us join David and Lisa in the celebration of their wedding and bring their happiness to a conclusion. --Church Bulletin Blooper -- http://mail.python.org/mailman/listinfo/python-list
Re: Overloading the tilde operator?
James Stroud <[EMAIL PROTECTED]> writes: > Ben Finney wrote: > > The Python runtime parser is designed to parse Python, not some > > arbitrary language that someone chooses to implement in Python. > > You haven't addressed why the limitation isn't arbitrary. Good thing I wasn't trying to do that, then. I was pointing out the source of the limitation. The Python syntax parser must follow the rules of the Python language. If you accept that premise, it follows that the '~' operator is unary only. If you *don't* accept that premise, I have no help to offer. -- \ "I cannot conceive that anybody will require multiplications at | `\ the rate of 40,000 or even 4,000 per hour ..." -- F. H. Wales, | _o__) 1936 | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Re: Overloading the tilde operator?
On Feb 2, 12:49 am, James Stroud <[EMAIL PROTECTED]> wrote: > Ben Finney wrote: > > > The Python runtime parser is designed to parse Python, not some > > arbitrary language that someone chooses to implement in Python. > > You haven't addressed why the limitation isn't arbitrary. Indeed, and that's because it is arbitrary. Python has the arbitrary limitation that it's not Perl (or C, or Lisp or what have you). George -- http://mail.python.org/mailman/listinfo/python-list
Re: Overloading the tilde operator?
Ben Finney wrote: > James Stroud <[EMAIL PROTECTED]> writes: > > >>Peter Otten wrote: >> >>>Chris wrote: >>> I am trying to overload the __invert__ operator (~) such that it can take a second argument, >>> >>x ~ x >>> >>> File "", line 1 >>>x ~ x >>> ^ >>>SyntaxError: invalid syntax >> >>Seems an arbitrary limitation. Consider >> - x >>and >> x - y > > > Both of which are meaningful syntax in Python, hence the Python parser > accepts them and knows what operations to call on the objects. > > >>Which is inconsistent with limiting ~ to a unary operation. > > > Which is the only Python-meaningful way to use that operator, and > translates to an appropriate call on the object. > > The Python runtime parser is designed to parse Python, not some > arbitrary language that someone chooses to implement in Python. > You haven't addressed why the limitation isn't arbitrary. You have only told us what we already know. So your argument, therefore, is not one. James -- http://mail.python.org/mailman/listinfo/python-list
Re: Overloading the tilde operator?
James Stroud <[EMAIL PROTECTED]> writes: > Peter Otten wrote: > > Chris wrote: > >>I am trying to overload the __invert__ operator (~) such that it > >>can take a second argument, > > > x ~ x > > File "", line 1 > > x ~ x > > ^ > > SyntaxError: invalid syntax > > Seems an arbitrary limitation. Consider >- x > and >x - y Both of which are meaningful syntax in Python, hence the Python parser accepts them and knows what operations to call on the objects. > Which is inconsistent with limiting ~ to a unary operation. Which is the only Python-meaningful way to use that operator, and translates to an appropriate call on the object. The Python runtime parser is designed to parse Python, not some arbitrary language that someone chooses to implement in Python. -- \ "You know what would make a good story? Something about a clown | `\who makes people happy, but inside he's real sad. Also, he has | _o__)severe diarrhea." -- Jack Handey | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Re: Overloading the tilde operator?
Peter Otten wrote: > Chris wrote: > > >>I am trying to overload the __invert__ operator (~) such that >>it can take a second argument, other than >>self, so that I can express: >> >>x ~ y >> >>by using: >> >>def __invert__(self, other): >> >>for example. Is this possible? > > > No, you will get a syntax error before python even look up the names: > > x > > Traceback (most recent call last): > File "", line 1, in ? > NameError: name 'x' is not defined > x ~ x > > File "", line 1 > x ~ x > ^ > SyntaxError: invalid syntax > > Peter Seems an arbitrary limitation. Consider - x and x - y Which is inconsistent with limiting ~ to a unary operation. James -- http://mail.python.org/mailman/listinfo/python-list
Re: Overloading the tilde operator?
Peter Otten: > No, you will get a syntax error before python even look up the names: There are some tricks that allow the use of "undefined" symbols in Python too, but they are probably just toys. I have recently posted a recipe in the cookbook for that. Bye, bearophile -- http://mail.python.org/mailman/listinfo/python-list
Re: Overloading the tilde operator?
Chris wrote: > I am trying to overload the __invert__ operator (~) such that > it can take a second argument, other than > self, so that I can express: > > x ~ y > > by using: > > def __invert__(self, other): > > for example. Is this possible? No, you will get a syntax error before python even look up the names: >>> x Traceback (most recent call last): File "", line 1, in ? NameError: name 'x' is not defined >>> x ~ x File "", line 1 x ~ x ^ SyntaxError: invalid syntax Peter -- http://mail.python.org/mailman/listinfo/python-list
Overloading the tilde operator?
I am trying to overload the __invert__ operator (~) such that it can take a second argument, other than self, so that I can express: x ~ y by using: def __invert__(self, other): for example. Is this possible? Thanks in advance, -- http://mail.python.org/mailman/listinfo/python-list
