before_match: before match

In nc: Named Capture to Data Tables

before match

Description

Augment pattern so that it can be used to match an entire string. Useful for complex find and replace operations, when used with capture_all_str.

Usage

before_match(...)

Arguments

...	pattern as in capture_first_vec.

Value

Pattern with two new groups, before (everything before ...) and match (text matching ... or blank for end of string).

Author(s)

Toby Hocking <[e-mail]> [aut, cre]

Examples

markdown_link <- list(
  "\\[",
  title=".*?",
  "\\]\\(",
  url="http.*?",
  "\\)")
markdown_subject <- "before [foo](http) between [bar text](http) after\n"
nc::capture_all_str(markdown_subject, markdown_link)

before_link <- nc::before_match(markdown_link)
(all_dt <- nc::capture_all_str(markdown_subject, before_link))

## before + match = full subject.
identical(all_dt[, paste(paste0(before, match), collapse="")], markdown_subject)

## replace with org link.
all_dt[, paste(paste0(before, ifelse(
  match=="", "", sprintf("[[%s][%s]]", url, title)
)), collapse="")]

## also works with no extra text before/after match.
nc::capture_all_str("[foo](http) between [bar text](http)", before_link)

nc documentation built on April 21, 2026, 9:06 a.m.