asdouble2.cpp

// [[Rcpp::plugins(cpp17)]]

#include <Rcpp.h>
#include <fast_float/fast_float.h>

// [[Rcpp::depends(RcppFastFloat)]]



// [[Rcpp::export]]
SEXP fastfloat_s(Rcpp::CharacterVector invec) {
  const auto n = invec.size();
  Rcpp::DoubleVector out(n, NA_REAL);
  double d;
  for (R_xlen_t i = 0; i < n; ++i)  {
    std::string s(invec[i]);
    auto res = fast_float::from_chars(s.data(), s.data() + s.size(), d);
    if (res.ec == std::errc()) {
      out[i] = d;
    }
  }
  return out;
}

// [[Rcpp::export]]
SEXP fastfloat_sv(Rcpp::CharacterVector invec) {
  const auto n = invec.size();
  Rcpp::DoubleVector out(n, NA_REAL);
  double d;
  for (R_xlen_t i = 0; i < n; ++i)  {
    std::string_view s(invec[i]);
    auto res = fast_float::from_chars(s.cbegin(), s.cend(), d);
    if (res.ec == std::errc()) {
      out[i] = d;
    }
  }
  return out;
}


#ifdef __cpp_lib_string_view
#include <string_view>
#endif

// [[Rcpp::export(as.double2)]]
SEXP fastfloat2(const Rcpp::CharacterVector invec) {
  const auto n = invec.size();
  Rcpp::DoubleVector out(n, NA_REAL);
  double d;
  bool any_failures = false;
  for (R_xlen_t i = 0; i < n; ++i)  {
#ifdef __cpp_lib_string_view
    std::string_view s(invec[i]);
    auto res = fast_float::from_chars(s.cbegin(), s.cend(), d);
#else
    std::string s(invec[i]);
    auto res = fast_float::from_chars(s.data(), s.data() + s.size(), d);
#endif
    if (res.ec == std::errc()) {
      out[i] = d;
    } else {
      any_failures = true;
    }
  }
  if (any_failures) {
    Rcpp::warning("NAs introduced by coercion");
  }
  return out;
}


/*** R
N <- 1e6
set.seed(42)
invec <- sample(sqrt(seq(1:N)))
input <- sample(
  c(rep(c("junk1", "junk2", "more junk!"), N, replace=T), as.character(invec))
)

suppressWarnings(
  microbenchmark::microbenchmark(
    as.double(input),
    fastfloat_s(input),
    fastfloat_sv(input),
    as.double2(input), # same as fastfloat_sv, w/ warn on failures
    check = "equal"
  )
)
#> Unit: milliseconds
#>                 expr      min       lq     mean   median       uq      max neval
#>     as.double(input) 779.2677 794.8253 815.7074 805.1494 836.4509 954.8745   100
#>   fastfloat_s(input) 201.6056 208.4925 229.3757 212.7901 245.5257 544.1641   100
#>  fastfloat_sv(input) 161.9853 168.6134 183.3555 171.3232 201.8738 487.4326   100
#>    as.double2(input) 161.8312 167.4808 186.2112 171.3153 201.8792 522.9541   100
*/