Jesus Cea Avion <jcea@argo.es> wrote in news:3E49069B.FBD8FA@argo.es:
>> OK, you want "lazy evaluation", but only in a very specific case.
>
> Specific but intuitive, useful and efficient, nevertheless.
One way to satisfy this would be to redefine setdefault something like
this:
def setdefault(aDict, aKey, aValue=None, lazy=None):
assert aValue is None or lazy is None
if aKey not in aDict:
aDict[aKey] = (if lazy is None: aValue else: lazy())
return aDict[aKey]
Then your existing calls continue to work, but you have the option of
specifying lazy evaluation, and the lazyness is clear at the point of call:
myDict.setdefault(myKey, lazy=lambda:expensive_function(args))
No new syntax required (ignoring the gratuitous 'if' expression).
If this every gets implemented, sentinal values would be better than None,
but I thought it better to keep the example simple.
I quite like Roman's idea for making lambda sometimes optional although
myDict.setdefault(myKey, lazy=:expensive_function(args))
could be confused with := assignment in other languages.
--
Duncan Booth duncan@rcp.co.uk
int month(char *p){return(124864/((p[0]+p[1]-p[2]&0x1f)+1)%12)["\5\x8\3"
"\6\7\xb\1\x9\xa\2\0\4"];} // Who said my code was obscure?
RetroSearch is an open source project built by @garambo | Open a GitHub Issue
Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo
HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4