| Title: | Round-Trip-Safe Double-Precision Formatting |
| Version: | 0.1.0 |
| Description: | Converts double-precision floating-point values to decimal strings with the shortest significands needed for round-trip recovery. Uses the 'zmij' algorithm through a vendored 'Rust' implementation. The method is described in Zverovich (2025), "Faster Double-to-String Conversion" https://vitaut.net/posts/2025/faster-dtoa/. Provides vectorized formatting, a correctly rounded inverse parser, and explicit handling of missing and non-finite values. |
| License: | MIT + file LICENSE |
| Copyright: | file inst/COPYRIGHTS |
| URL: | https://nanx.me/zmij/, https://github.com/nanxstats/zmij |
| BugReports: | https://github.com/nanxstats/zmij/issues |
| Encoding: | UTF-8 |
| Depends: | R (≥ 4.2) |
| Suggests: | testthat (≥ 3.0.0) |
| SystemRequirements: | Cargo (Rust's package manager), rustc >= 1.71.0, xz |
| Config/rextendr/version: | 0.5.0 |
| Config/testthat/edition: | 3 |
| RoxygenNote: | 8.0.0 |
| NeedsCompilation: | yes |
| Packaged: | 2026-07-24 04:01:45 UTC; nanx |
| Author: | Nan Xiao  [aut,
cre, cph],
David Tolnay [ctb, cph] (Author of the vendored Rust zmij crate),
Victor Zverovich [ctb, cph] (Author of the zmij algorithm and original
C++ implementation) |
| Maintainer: | Nan Xiao <me@nanx.me> |
| Repository: | CRAN |
| Date/Publication: | 2026-08-04 16:20:02 UTC |
Format Double-Precision Values with zmij
Description
Convert numeric values to decimal strings with the shortest significands that recover the original IEEE 754 binary64 values when parsed using round-to-nearest, ties-to-even rounding.
Usage
format_double(x)
Arguments
x |
A numeric vector, matrix, or array. |
Details
Integer inputs are converted to double precision before formatting. zmij uses fixed notation for decimal exponents from -5 through 15 and scientific notation outside that range. Other attributes, including classes, are not retained because the returned values are character strings.
Value
A character vector with the same length and shape as x. Names and
dimensions are preserved. Missing values remain NA; NaN, positive
infinity, and negative infinity become "NaN", "inf", and "-inf",
respectively.
References
Zverovich V (2025). "Faster double-to-string conversion." https://vitaut.net/posts/2025/faster-dtoa/.
Tolnay D. "zmij: A double-to-string conversion algorithm based on Schubfach." https://github.com/dtolnay/zmij.
Examples
x <- c(pi, 0.1, -0, .Machine$double.xmin, .Machine$double.xmax)
formatted <- format_double(x)
formatted
identical(parse_double(formatted), x)
format_double(c(NA_real_, NaN, Inf, -Inf))
Parse Double-Precision Strings
Description
Parse decimal strings into IEEE 754 binary64 values using Rust's correctly
rounded parser. This is the inverse of format_double() for every finite
double.
Usage
parse_double(x)
Arguments
x |
A character vector, matrix, or array. |
Details
The parser accepts decimal and scientific notation, along with "NaN",
"inf", and "-inf". Leading or trailing whitespace and other invalid
strings cause an error that identifies the first invalid element.
Using parse_double() avoids platform-specific edge cases in R's built-in
decimal parser near the limits of the binary64 range.
Value
A double vector with the same length and shape as x. Names and
dimensions are preserved. Missing strings remain NA_real_.
Examples
x <- c(pi, 0.1, -0, .Machine$double.xmin, .Machine$double.xmax)
identical(parse_double(format_double(x)), x)
parse_double(c("1.5", "3e-1", NA_character_, "inf"))