Encode and decode text

naxp_encode() encodes text as encoded values under a naxp, and naxp_decode() decodes them back to the canonical form of the text.

Usage

naxp_encode(text, naxp)

naxp_decode(x, naxp = NULL)

Arguments

text

A character vector.

naxp

A naxp from naxp_parse(), a pattern string or a naxp_encoded vector, whose naxp is used. For naxp_decode(), it is needed only where x is not a naxp_encoded vector.

x

A naxp_encoded vector, or an integer or double vector of encoded values. Bare values must be whole numbers from 0 to the naxp's maximum encoded value, or NA.

Value

• naxp_encode(): a naxp_encoded vector the same length as text, with its names.

• naxp_decode(): a character vector the same length as x, with its names, holding NA where a value is 0 or NA.

Details

Each text a naxp accepts encodes to a whole number from 1 to its maximum encoded value. Several texts may share a value, such as a postcode written with and without a space, and each value decodes to one canonical form.

Text the naxp does not accept is invalid and encodes to 0, as in every naxp library. So does NA, and so does any text that is not ASCII, whatever its marked encoding. Encoded values are never NA. naxp_decode() returns NA for 0, because no other string can stand for it: a naxp may accept the empty string.

Encoded values are held as integers where the naxp's maximum encoded value is at most 2^31 - 1, and as doubles where it is at most 2^53. Above 2^53, which is the largest whole number R holds exactly, both functions raise an error.

See also

naxp_accepts() and naxp_canonical_form() to check text without encoding it.

Examples

nl_postcode <- naxp_parse(r"(\9\9\9\9 \s!! \A\A)")

codes <- naxp_encode(c("1012AB", "1012 AB", "not a postcode"), nl_postcode)
codes
#> <naxp_encoded[3]> \9\9\9\9 \s!! \A\A
#> [1] 1012 AB       1012 AB       <invalid (0)>
as.integer(codes)
#> [1] 684114 684114      0

naxp_decode(codes)
#> [1] "1012 AB" "1012 AB" NA       
naxp_decode(684114L, nl_postcode)
#> [1] "1012 AB"