Introduction
STL provides a lot of useful utilities. They can be used to implement interesting functions.
- This is a collection of this *
Count lines
int count_lines(string& file) {
auto fd = ifstream(file.c_str();
return count_if(
istreambuf_iterator<char>(fd),
istreambuf_iterator<char>(),
[](c)->bool {return c == '\n';}
):
}
Please note that: istream_iterator won’t work here. Stackoverflow
Normally when you care:
- formatted output, e.g. int/double, then use
istream_iterator - unformatted input, raw bytes, use
istreambuf_iterator
The same applies to ostream_iterator and ostreambuf_iterator.
String trim
void trim_left(string& input, function<bool(char)> fn) {
input.erase(
input.begin(),
find_if(input.begin(), input.end(), [&](char c) {return !fn(c);})
);
}
void trim_right(string& input, function<bool(char)> fn) {
input.erase(
find_if(input.rbegin(), input.rend(), [&](char c) {return !fn(c);}).base(),
input.end()
);
}
The base() function call is used to get the underlying iterator.
string a = "";
std::reverse_iterator<std::string::iterator> ite = a.rbegin();
Convert case
string to_upper(string input) {
transform(input.begin(), input.end(), ::toupper);
return input;
}
string to_lower(string input) {
transform(input.begin(), input.end(), ::tolower);
return input;
}
Split and Join strings
Filter
template<typename Iterator, typename Pred>
void filter(Iterator beg, Iterator end, Iterator out, Pred p) {
copy_if(beg, end, out, p);
}
Map
template<typename Iterator, typename Proc>
void map(Iterator beg, Iterator end, Iterator out, Proc p) {
transform(beg, end, out, p);
}
Reduce
template<typename Iterator, typename Reduce, typename T>
T reduce(Iterator beg, Iterator end, T initial, Reduce r) {
return accumulate(beg, end, initial, r);
}