node-get-match: Get the match(es) from a meta-variable

In astgrepr: Parse and Manipulate R Code

Get the match(es) from a meta-variable

Description

Those functions extract the content of the meta-variable specified in node_find():

• node_get_match() is used when the meta-variable refers to a single pattern, e.g. ⁠"plot($A)⁠;

• node_get_multiple_matches() is used when the meta-variable captures all elements in a pattern, e.g. "plot($$$A)".

Usage

node_get_match(x, meta_var)

node_get_multiple_matches(x, meta_var)

Arguments

x	A node, either from tree_root() or from another ⁠node_*()⁠ function.
meta_var	The name given to one of the meta-variable(s) in node_find().

Value

node_get_match() returns a list of depth 1, where each element is the node corresponding to the rule passed (this can be of length 0 if no node is matched). node_get_multiple_matches() also returns a list of depth 1, but each element can contain multiple nodes when the meta-variable captures all elements in a pattern.

Examples

src <- "x <- rnorm(100, mean = 2)
    plot(mtcars)"

root <- src |>
  tree_new() |>
  tree_root()

# we capture a single element with "$A" so node_get_match() can be used
root |>
  node_find(ast_rule(pattern = "plot($A)")) |>
  node_get_match("A")

# we can specify the variable to extract
root |>
  node_find(ast_rule(pattern = "rnorm($A, $B)")) |>
  node_get_match("B")

# we capture many elements with "$$$A" so node_get_multiple_matches() can
# be used here
root |>
  node_find(ast_rule(pattern = "rnorm($$$A)")) |>
  node_get_multiple_matches("A")

astgrepr documentation built on June 8, 2025, 11:05 a.m.