Thanks Marshall for the reply. In our code I faced a strange error when splitting the string. The hyphen symbol was used to represent null data, upon splitting the string containing only hyphen, I expected a result of zero tokens (I was wrong here). Even dynamic languages are behaving same, see below a python sample, Python 2.7.6 (default, Mar 22 2014, 22:59:56) [GCC 4.8.2] on linux2 Type "help", "copyright", "credits" or "license" for more information.
s = "-Foo" tokens = s.split("-") print tokens ['', 'Foo']
An example in the boost documentation would help the user. Even the following command line example proves the same, $echo "a-b" | awk -F "-" '{for (i=1; i <= NR; i++) printf "%s:", $i}' ---> This will print a:b $echo "-" | awk -F "-" '{for (i=1; i <= NR; i++) printf "%s:", $i}' ---> This will print : (i.e. two NUL strings on screen) Infact the second command line example was the reason behind my confusion :) Thankful to you all Boost developers. Great work. On Thu, May 21, 2015 at 1:59 AM, Marshall Clow <mclow.lists@gmail.com> wrote:
On Wed, May 20, 2015 at 11:32 AM, Venkateswara Rao Sanaka < moderncpp.venki@gmail.com> wrote:
Hi,
I am getting two empty strings from the following program,
void boost_split_test() {
const string &text("-");
vector<string> tokens;
split(tokens, text, boost::is_any_of("-"), token_compress_on);
cout << "size of tokens " << tokens.size() << '\n';
for (auto const &e : tokens)
cout << e.size() << '\n';
}
Output:
size of tokens 2 0 0
Is this expected output? I expecting an zero split parts. Could someone clarify?
This seems reasonable to me.
You asked it to split the string containing a single dash into parts separated by dashes. The string gets split into an empty string, a dash (which is not returned to you, being the separator), and an empty string.
Consider splitting the input string "Foo-" (or "-Foo") compared to "Foo". One gives two strings (one before the dash, one after the dash), the other gives one string (because there are no dashes).
Given a string with "n" separators, you should get "n+1" strings back (with the proviso that consecutive separators are collapsed together, so "Foo--" is treated the same as "Foo-").
-- Marshall
P.S. Checking the tests, I notice that there's no coverage for this case (separators at the beginning or the end of the input). I'll put it on my list. Thanks!
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-- Thanks, :) Venki.