Stan Schymanski wrote:
> Hi Jason,
>
> That's awesome, thanks a lot! I had a bit of trouble understanding the
> documentation of partial, but your example helped tremendously. This
> should definitely be included in any upcoming documentation on
> fast_float. As far as I understand, partial(F,1) just replaces the first
> variable in F by 1. If I define something like F = fast_float(a*x^3 +
> b*x^2 + c*x + d, 'a', 'b', 'c', 'd', 'x'), could I then use partial to
> replace a, b, d and x and leave c as a variable, or would I have to
> re-define F to take c as the last argument?
>
Apparently fast_float things don't take keyword arguments, so you have
to use a lambda function (that will take keyword arguments) to put
things in the right order.
sage: var('a,b,c,d,x')
(a, b, c, d, x)
sage: F = fast_float(a*x^3 + b*x^2 + c*x + d, 'a', 'b', 'c', 'd', 'x')
sage: ff=partial(lambda a,b,c,d,x: F(a,b,c,d,x), a=1,b=2,d=5,x=-2)
sage: ff(c=3)
-1.0
alternatively, since arguments to gg (below) are just appended to the
non-keyword arguments, you can have one "hole" in the non-keyword
arguments. To have more than this, you need to do something more special.
sage: gg=partial(lambda a,b,c,d,x: F(a,b,c,d,x), 1,2,d=5,x=-2)
sage: gg(3)
-1.0
It would be nice (and pretty straightforward to write) a partial
function that took a dictionary like:
partial(f, {0: 10, 'x': 3, 2: 20})
which would make a function that behaved like:
f(10, *, 20, *args, x=3)
(i.e., the keys above are the places in the non-keyword arguments; since
we don't have a value specified for the position 1 in the non-keyword
arguments, it is left blank.) Then your example above would be
something like:
sage: ff=partial(F, {0:1, 1: 2, 4: 5, 5: -2})
sage: ff(3)
-1.0
Thanks,
Jason
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