Ka-Ping Yee's suggestion of overriding the interpolation builtin (or
let's say, the "%" operator used for formatting) means there might be
another way to do this using GFs: let's say that the following
illustrative snippet is still desirable -
On Wed, 6 Dec 2006, Jan Grant wrote:
> def foo(d: sqlDriver):
> s = "select template goes here" % (param1, param2)
> r = d.query(s) # do the Right Thing
Suppose for a moment that % used like this returns, not a string, but an
object that encapsulates the format and the parameter set supplied.
Then the sqlDriver implementation could take advantage of Phillip's GF
mechanisms thus:
class driver # which implements sqlDriver
def query(self, s: str):
... code here to perform a query based on a stock string ...
def query(self, pf: parameterised_format):
... code here to extract the format string and quote the
... parameters appropriately within it.
The _cost_ of this mechanism is that all library functions potentially
have to become aware of the parameterised_format type. Alternatively
(and although explicit is better than implicit), a GF framework might
look to coerce a parameterised_format into a str using something like
adaption. Or "parameterised_format" could be a _subtype_ of "str", which
behaves exactly like the str type if it is naively used in contexts
which demand a plain string. In the latter case (if achievable, I have
not examined this closely) a %-formatted object would "degrade" to the
simple string case for most current uses.
jan
--
jan grant, ISYS, University of Bristol. http://www.bris.ac.uk/
Tel +44 (0)117 3317661 http://ioctl.org/jan/
perl -e 's?ck?t??print:perl==pants if $_="Just Another Perl Hacker\n"'
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