On 26 Apr 2009, at 21:20, Larry Hastings wrote:
Anyway, this is one reason why I like the "do:" statement I proposed. (The other one--the one where I also proposed "continue if" and "break if". But given your reaction to those let's ignore 'em for now.) This isn't *pure* sugar--it's a mildly novel flow control construct for structured programming. Certainly Python doesn't have anything like it right now; "while True:" isn't an exact match (and "while False:" is equivalent to "if 0:"). My "do:" would allow spelling do/while as:
do: something() if condition: continue
I think that's a reasonable do/while, and so economical: we only added one new keyword. This form of "do:" has other uses too, as per my previous email.
Not that I expect this syntax to take the world by storm.
It's funny because I had something like this in mind when I myself suggested 'break if ...' and 'continue if ...' a little while ago (although I would go for a 'loop:' that doesn't need to be continue'd explicitely). I had come to the point of view that the restrictions of the looping construct had in fact somehow liberated it and made it more versatile by making if condition: break and if condition: continue common control flow constructs inside a while loop, that in particular encompass the do ... while / repeat ... until constructs, etc seen in other languages (I may have expressed myself better in the original thread). My motivation for 'break/continue if ...' was that it would make those constructs stand out more (and could be hilighted clearly as such in editors) - I was a bit surprised when I was told it would make code less readable and that it was a slippery slope, but then I have lots of ideas, most of which don't turn out to be very good :) -- Arnaud