On 05/04/2011 01:07 AM, Greg Ewing wrote:
mark florisson wrote:
cdef func(floating x, floating y):
...
you get a "float, float" version, and a "double, double" version, but
not "float, double" or "double, float".
It's hard to draw conclusions from this example because
it's degenerate. You don't really need multiple versions of a
function like that, because of float <-> double coercions.
A more telling example might be
cdef double dot_product(floating *u, floating *v, int length)
By your current rules, this would give you one version that
takes two float vectors, and another that takes two double
vectors.
But if you want to find the dot product of a float vector and
a double vector, you're out of luck.
First, I'm open for your proposed syntax too...But in the interest of
seeing how we got here:
The argument to the above goes that you *should* be out of luck. For
instance, talking about dot products, BLAS itself has float-float and
double-double, but not float-double AFAIK.
What you are saying that this does not have the full power of C++
templates. And the answer is that yes, this does not have the full power
of C++ templates.
At the same time we discussed this, we also discussed better support for
string-based templating languages (so that, e.g., compilation error
messages could refer to the template file). The two are complementary.
Going back to Greg's syntax: What I don't like is that it makes the
simple unambiguous cases, where this would actually be used in real
life, less readable.
Would it be too complicated to have both? For instance;
i) You are allowed to use a *single* fused_type on a *function*
without declaration.
def f(floating x, floating *y): # ok
Turns into
def f[floating T](T x, T *y):
This is NOT ok:
def f(floating x, integral y):
# ERROR: Please explicitly declare fused types inside []
ii) Using more than one fused type, or using it on a cdef class or
struct, you need to use the [] declaration.
Finally: It is a bit uncomfortable that we seem to be hashing things out
even as Mark is implementing this. Would it be feasible to have a Skype
session sometimes this week where everybody interested in the outcome of
this come together for an hour and actually decide on something?
Mark: How much does this discussion of syntax impact your development?
Are you able to treat them just as polish on top and work on the
"engine" undisturbed by this?
Dag Sverre
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