David Abrahams wrote:
"Eric Niebler" <eric@boost-consulting.com> writes:
OK, I'll hold off on filing a DR until we have some recommendations.
Suggestion: don't keep this under your hat. At least alert the LWG and say that you will have recommendations in a few days.
That's probably good advice. I've sent a DR to comp.std.c++. Also, I may have found another issue, closely related to the one under discussion. It regards case-insensitive matching of named character classes. The regex_traits<> provides two functions for working with named char classes: lookup_classname and isctype. To match a char class such as [[:alpha:]], you pass "alpha" to lookup_classname and get a bitmask. Later, you pass a char and the bitmask to isctype and get a bool yes/no answer. But how does case-insensitivity work in this scenario? Suppose we're doing a case-insensitive match on [[:lower:]]. It should behave as if it were [[:lower:][:upper:]], right? But there doesn't seem to be enough smarts in the regex_traits interface to do this. Imagine I write a traits class which recognizes [[:fubar:]], and the "fubar" char class happens to be case-sensitive. How is the regex engine to know that? And how should it do a case-insensitive match of a character against the [[:fubar:]] char class? John, can you confirm this is a legitimate problem? I see two options: 1) Add a bool icase parameter to lookup_classname. Then, lookup_classname( "upper", true ) will know to return lower|upper instead of just upper. 2) Add a isctype_nocase function I prefer (1) because the extra computation happens at the time the pattern is compiled rather than when it is executed. -- Eric Niebler Boost Consulting www.boost-consulting.com