Jason Grout wrote:
> kcrisman wrote:
>
>> On Dec 14, 9:19 am, Carlos Córdoba <ccordob...@gmail.com> wrote:
>>
>>> I don't think it would be so hard to do but this could break
>>> interoperability with Python, the language on which Sage is based. Besides
>>> it could make Sage like a dialect of python, something that sage devs don't
>>> want to do.
>>>
>>> Unfortunately python is not a very friendly functional programming
>>> language, although it has some constructs that can help you if you like to
>>> do things in the functional style.
>>>
>>> Hope this helps,
>>> Carlos
>>>
>>> 2009/12/13 Alasdair <amc...@gmail.com>
>>>
>>>
>>>
>>>
>>>> In some CAS's (Sage, Maxima), the "lambda" construct is used for an
>>>> anonymous function:
>>>> p=prime_range(30)
>>>> map(lambda x:x^2+1,p)
>>>> whereas in others, an arrow notation is used:
>>>> map(x->x^2+1,p) (Maple, MuPAD)
>>>> map(x+->x^2+1,p) (Axiom)
>>>> I'm very fond of the convenience of arrow notation. Would it be very
>>>> hard to incorporate such a notation into the Sage parser?
>>>>
>> If this would cause a Python syntax error, then presumably foo -> bar
>> could be turned into lambda foo: bar, which would be completely
>> native. Perhaps someone who is quite familiar with the preparser will
>> comment. But this seems like a reasonable thing to add, particularly
>> for those coming from Maple. What does Mathematica do for such
>> anonymous functions (if anything)?
>>
>
>
> It looks like -> might cause a syntax error, at least in a trivial case:
>
> sage: x -> x^2
> ------------------------------------------------------------
> File "<ipython console>", line 1
> x -> x**Integer(2)
> ^
> SyntaxError: invalid syntax
>
>
> We currently print out things in sort of functional notation:
>
> sage: f(x)=x^2
> sage: f
> x |--> x^2
>
> I don't know if it's a good idea to make this valid Sage syntax, though.
> I'm on the fence, but leaning towards not favoring it just because
> of the added complexity and the departure from true Python, and the
> python version isn't all that bad.
>
Note that -> gets a meaning in Python 3, to annotate the result of a
function:
def foo(a: int) -> float:
...
I don't think this is a technical problem as one can rely on the
statement to start with "def", but at least -> already means something.
Dag Sverre
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