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Select Line Indices Based on Numeric Positions or Regex Delimiters

dot-grep_lines.Rd

Computes a vector of line indices either directly from numeric input or by identifying a contiguous block of lines delimited by regular expression matches.

Usage

.grep_lines(x, lines = NULL)

Arguments

x

A character vector, typically representing lines of text.

lines

Either:

  • A numeric vector of line indices, or

  • A character vector of length 1 specifying regex delimiters in the form "start|end".

Value

A numeric vector of line indices.

Details

If lines is numeric, it is returned as-is. If lines is a character string, it must be a single regex of the form "start|end", where start and end are regular expressions matched against x. The returned indices span from the first match of start to the first match of end (inclusive). If only one regex is provided, it is used for both start and end.

When lines is NULL, the function currently returns 1:length(lines), which evaluates to an empty integer vector.

Examples

txt <- c("alpha", "start", "beta", "gamma", "end", "delta")

.grep_lines(txt, c(2, 3, 4))
#> [1] 2 3 4
.grep_lines(txt, "start|end")
#> [1] 2 3 4 5
.grep_lines(txt, "beta")
#> [1] 3