R: Turn an expression to a label

expr_label {rlang} | R Documentation

## 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.

### 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)
    })))

[Package rlang version 1.0.2 Index]