Clarification of https://twitter.com/klmr/status/963788075339075584

problems.md

• Invalid signature void main() (… I mean, seriously?!)
• Missing namespace qualifiers throughout
• Missing include for accumulate
• Missing ) in accumulate call
• Invalid arguments to accumulate call:
  • init missing
  • op has wrong function type (expected (T, T) -> T; got (T) -> void)
  • — in fact, it seems they actually meant std::for_each.
• … but using std::accumulate correctly would have been way easier, without a gratuitous lambda.
• Expensive copy of base_quals() (this should absolutely be captured by const-ref)
• Inconsistent indentation
• Misleading variable naming: abq is a sum, not an average, of base qualities.
• Unused, gratuitous constant declaration
• Expensive endl instead of '\n'

Here’s a cleaned up version:

#include "gamgee/gamgee.h"
#include <iostream>
#include <numeric>

int main() {
    for (auto const& record : gamgee::SingleSamReader("input.bam")) {
        auto const& bqs = record.base_quals();
        auto const sum_qual = std::accumulate(bqs.begin(), bqs.end(), 0.0);
        std::cout << sum_qual / bqs.size() << "\n";
    }
}