rlang (version 0.0.0.9000)

expr_label: Turn an expression to a label.

Description

expr_text() turns the expression into a single string; expr_label() formats it nicely for use in messages.

Usage

expr_label(expr)
expr_text(expr, width = 60L, nlines = Inf)

Arguments

expr

An expression to labellise.

width

Width of each line.

nlines

Maximum number of lines to extract.

Examples

# To labellise a function argument, first capture it with
# substitute():
fn <- function(x) expr_label(substitute(x))
fn(x:y)

# Strings are encoded
expr_label("a\nb")

# Names and expressions are quoted with ``
expr_label(quote(x))
expr_label(quote(a + b + c))

# Long expressions are collapsed
expr_label(quote(foo({
  1 + 2
  print(x)
})))