parsetools (version 0.1.1)

assignments: Assignment Node Navigation.

Description

These function help identify and navigate assignments in parse data.

Usage

pd_is_assignment(id, pd, .check = TRUE)
pd_get_assign_value_id(id, pd, .check = TRUE)
pd_get_assign_variable_id(id, pd, .check = TRUE)

Arguments

id

id of the expression of interest

pd

The parse-data information

.check

Perform checks for input validation?

Functions

• pd_is_assignment: Check if the node is an assignment expression.

• pd_get_assign_value_id: Get the id for the value portion of an assignment.

• pd_get_assign_variable_id: Get the variable of an assignment.

Details

These functions only deal with assignment operators. Using base::assign() or base::delayedAssign() are considered calls in terms of parse data.

There are five assignment operators grouped into three categories.

• Left assignment, the <- and <<-,

• right assignment, -> and the rarely used ->>

• and the equals assignment =.

Examples

# NOT RUN {
# load example file and get_parse data
ex.file <- system.file("examples", "example.R", package="parsetools")
exprs <- parse(ex.file, keep.source = TRUE)
pd <- get_parse_data(exprs)

# There are 3 expressions so there should be three roots.
sum(pd_is_root(pd$id, pd))
roots <- pd_all_root_ids(pd)

# The first should be an assignment
pd_is_assignment(roots[[1]], pd=pd)

# the variable/value of the assignment can be accessed by
variable.id <- pd_get_assign_variable_id(roots[[1]], pd)
value.id <- pd_get_assign_value_id(roots[[1]], pd)
# Note that these function will give the variable/value part
# for both LEFT_ASSIGN and RIGHT_ASSIGN operators, going by order
# of ids, or position in the data may not give the expected results.
# }