Matching "beginning-of-line" using libc++ regex library (C++11)
c++, c++11, clang, libc++, regex
Solution
I've looked over all of the relevant standards, and as far as I can tell, ^ matches only the beginning of the string, and not a newline, unless the engine is in multiline mode. The default engine is ECMA-262 The engine is not in multiline mode by default, and I see no way to put it into multiline mode using the std C++ interface.
All that being said, if someone can point me towards normative text that says differently, I'll consider this a bug report and do my best to fix it.
Problem
I would like to match all lines that start with a given word, say iheap. If I am not mistaken the regular expression (in ECMAScript syntax) `"^iheap.*"` should do the trick. However, when I tested this in C++11 using libc++'s regex library, only the first line is matched. So `"^..."` seems to only match beginning-of-input instead of beginning-of-line. Here is an example: ``` #include <string> #include <regex> #include <iostream> using namespace std; int main() { regex rx("^iheap.*"); string s = "iheap says hello.\niheap says hello again.\n"; cout << s << regex_replace(s, rx, "IHEAP"); return 0; } ``` Output: ``` iheap says hello. iheap says hello again. IHEAP iheap says hello again. ``` Is this a bug of libc++ or am I doing something wrong? Thanks! Note: I am using Mac OS X Mountain Lion and Apple LLVM Compiler 4.0 (basically a snapshot of clang 3.1 SVN).