Visualize Regular Expressions

Usage

explain(pattern, open = FALSE, print = TRUE, dictionary = getOption("regex.library"))

Arguments

pattern

A character string containing a regular expression or a character string starting with "@" that is a regular expression from a qdapRegex dictionary.

open

logical. If TRUE the default browser will attempt to open http://www.regexper.com page. Setting open = 2 will utilize an unstable visualization via https://www.debuggex.com. This approach utilizes a non-api scrape that is subject to change and not guaranteed to be stable. The regex is set to Python flavor which handles lookbehinds that the Java based http://www.regexper.com does not. This functionality was developed by Matthew Flickinger (see http://stackoverflow.com/a/27574103/1000343 for details). Note that the user must have httr installed or will be prompted if the package cannot be required.

print

logical. Should explain print output to the console?

dictionary

A dictionary of canned regular expressions to search within.

Examples

explain("\\s*foo[A-Z]\\d{2,3}")

NODE                     EXPLANATION
--------------------------------------------------------------------------------
  \\s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  foo                      'foo'
--------------------------------------------------------------------------------
  [A-Z]                    any character of: 'A' to 'Z'
--------------------------------------------------------------------------------
  \\d{2,3}                  digits (0-9) (between 2 and 3 times
                           (matching the most amount possible))


explain("@rm_time")

NODE                     EXPLANATION
--------------------------------------------------------------------------------
  \\d{0,2}                  digits (0-9) (between 0 and 2 times
                           (matching the most amount possible))
--------------------------------------------------------------------------------
  :                        ':'
--------------------------------------------------------------------------------
  \\d{2}                    digits (0-9) (2 times)
--------------------------------------------------------------------------------
  (?:                      group, but do not capture (optional
                           (matching the most amount possible)):
--------------------------------------------------------------------------------
    [:.]                     any character of: ':', '.'
--------------------------------------------------------------------------------
    \\d+                      digits (0-9) (1 or more times (matching
                             the most amount possible))
--------------------------------------------------------------------------------
  )?                       end of grouping


## <strong>Not run</strong>: 
# explain("\\s*foo[A-Z]\\d{2,3}", open = TRUE)
# explain("@rm_time", open = TRUE)
# ## <strong>End(Not run)</strong>

See also

Author