Turn an expression to a label — expr

expr_text() turns the expression into a single string, which might be multi-line. expr_name() is suitable for formatting names. It works best with symbols and scalar types, but also accepts calls. expr_label() formats the expression nicely for use in messages.

expr_label(expr)

expr_name(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.

Life cycle

These functions are in the questioning stage because they are redundant with the quo_ variants and do not handle quosures.

Examples

# To labellise a function argument, first capture it with
# substitute():
fn <- function(x) expr_label(substitute(x))
fn(x:y)
#> [1] "`x:y`"

# Strings are encoded
expr_label("a\nb")
#> [1] "\"a\\nb\""

# Names and expressions are quoted with ``
expr_label(quote(x))
#> [1] "`x`"
expr_label(quote(a + b + c))
#> [1] "`a + b + c`"

# Long expressions are collapsed
expr_label(quote(foo({
  1 + 2
  print(x)
})))
#> [1] "`foo(...)`"