It might be good to include opt<> (optional) in the library, or to have a short cookbook of common patterns like this, since it is not always obvious if one is doing the right thing. I've been thinking a lot about whether I should add something like opt<> to the library or not given that it is a common pattern in grammars. The reason I have not done it yet was that I could not come up with a reasonable Default value and having two arguments (the optional parser and what to return when it is not present) didn't look simpler to me
Hi Gordon, On 2015-06-04 08:07, Gordon Woodhull wrote: than the one_of<, return_<>> pattern. However, given that people seem to create opt anyway (as you did it as well) suggests that it should still be added. Regards, Ábel