Candidate format strings for parsing time

Combines one or more format strings into a character vector for use as the format argument of time_parse(). When multiple format strings are given, time_parse() tries each in turn and keeps whichever parses the most values, so parse_format() is the usual way to build up a set of candidates to try (it's also how chronon_parse_linear()/ chronon_parse_cyclical() methods build theirs). It can optionally mark its candidates as using regex syntax rather than literal text; see the regex argument below.

Usage

parse_format(..., regex = FALSE)

Arguments

...

Format strings, as for the format argument of time_parse().

regex

Whether the literal (non-token) text in ... should be matched as regular expression syntax rather than escaped literally (e.g. "[/-]" to accept either / or - as a separator). This is a niche option for irregular text - most formats leave it at the default, FALSE. See the regex argument of time_parse() for details.

Value

A character vector of format strings suitable for time_parse(), with a "regex" attribute for the regex argument the parser.

See also

time_parse() for using the result as format, chronon_parse_linear()/chronon_parse_cyclical() for calendar-specific candidates built this way.

Examples

parse_format("{lin(year)}-{cyc(month, year)}-{cyc(day, month)}")
#> [1] "{lin(year)}-{cyc(month, year)}-{cyc(day, month)}"
#> attr(,"regex")
#> [1] FALSE

# Multiple candidates are tried in turn, keeping whichever parses most values
parse_format(
  "{lin(year)}-{cyc(month, year)}-{cyc(day, month)}",
  "{lin(year)}/{cyc(month, year)}/{cyc(day, month)}"
)
#> [1] "{lin(year)}-{cyc(month, year)}-{cyc(day, month)}"
#> [2] "{lin(year)}/{cyc(month, year)}/{cyc(day, month)}"
#> attr(,"regex")
#> [1] FALSE

# regex = TRUE treats the surrounding text as regular expression syntax
parse_format(
  "{lin(year)}[/-]{cyc(month, year)}[/-]{cyc(day, month)}",
  regex = TRUE
)
#> [1] "{lin(year)}[/-]{cyc(month, year)}[/-]{cyc(day, month)}"
#> attr(,"regex")
#> [1] TRUE