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expr_label
Turn an expression to a label
Description
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.
Usage
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)
# 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)
})))