Re: check if line is whitespace
On Sep 3, 7:21 pm, puzzlecracker <ironsel2...@gmail.com> wrote:
What is the quickest way to check that the following:
const line[127]; only contains whitespace, in which case to ignore it.
You mean std::string line, don't you. The above isn't a legal
C++ declaration.
something along these lines:
isspacedLine(line);
Well, the standard library already has direct support for this,
but it's interface isn't the most friendly. But something like
the following should do the trick:
bool
isOnlySpaces(
std::string const& line,
std::locale const& locale = std::locale() )
{
return std::use_facet< std::ctype< char > >( locale )
.scan_not( std::ctype_base::space,
line.data(), line.data() + line.size() )
== line.data() + line.size() ;
}
(If you're forced to use arrays of char, instead of string, this
solution still works perfectly well.)
More generally, however, I tend to use regular expressions in
such cases. If the line matches "^[:space:]*$", ignore it.
With a good implementation of regular expressions (which uses a
DFA if the expression contains no extensions), this can be just
as fast as the above, if not faster. (Just make sure you only
construct the regular expression once, and not every time you
call the function.
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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