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Format quosures for printing or labelling

Source: R/quo.R
quo_label.Rd

[Superseded]

Note: You should now use as_label() or as_name() instead of quo_name(). See life cycle section below.

These functions take an arbitrary R object, typically an expression, and represent it as a string.

  • quo_name() returns an abbreviated representation of the object as a single line string. It is suitable for default names.

  • quo_text() returns a multiline string. For instance block expressions like { foo; bar } are represented on 4 lines (one for each symbol, and the curly braces on their own lines).

These deparsers are only suitable for creating default names or printing output at the console. The behaviour of your functions should not depend on deparsed objects. If you are looking for a way of transforming symbols to strings, use as_string() instead of quo_name(). Unlike deparsing, the transformation between symbols and strings is non-lossy and well defined.

Usage

quo_label(quo)

quo_text(quo, width = 60L, nlines = Inf)

quo_name(quo)

Arguments

quo

A quosure or expression.

width

Width of each line.

nlines

Maximum number of lines to extract.

Life cycle

These functions are superseded.

  • as_label() and as_name() should be used instead of quo_name(). as_label() transforms any R object to a string but should only be used to create a default name. Labelisation is not a well defined operation and no assumption should be made about the label. On the other hand, as_name() only works with (possibly quosured) symbols, but is a well defined and deterministic operation.

  • We don't have a good replacement for quo_text() yet. See https://github.com/r-lib/rlang/issues/636 to follow discussions about a new deparsing API.

See also

expr_label(), f_label()

Examples

# Quosures can contain nested quosures:
quo <- quo(foo(!! quo(bar)))
quo
#> <quosure>
#> expr: ^foo(^bar)
#> env:  0x556762617680

# quo_squash() unwraps all quosures and returns a raw expression:
quo_squash(quo)
#> foo(bar)

# This is used by quo_text() and quo_label():
quo_text(quo)
#> [1] "foo(bar)"

# Compare to the unwrapped expression:
expr_text(quo)
#> [1] "~foo(~bar)"

# quo_name() is helpful when you need really short labels:
quo_name(quo(sym))
#> [1] "sym"
quo_name(quo(!! sym))
#> [1] "function (x) ..."