R: Examples for 'rlang::is

### ** Examples

is_formula(~10)

[1] TRUE

is_formula(10)

[1] FALSE

# If you don't supply `lhs`, both one-sided and two-sided formulas
# will return `TRUE`
is_formula(disp ~ am)

[1] TRUE

is_formula(~am)

[1] TRUE

# You can also specify whether you expect a LHS:
is_formula(disp ~ am, lhs = TRUE)

[1] TRUE

is_formula(disp ~ am, lhs = FALSE)

[1] FALSE

is_formula(~am, lhs = TRUE)

[1] FALSE

is_formula(~am, lhs = FALSE)

[1] TRUE

# Handling of unevaluated formulas is a bit tricky. These formulas
# are special because they don't inherit from `"formula"` and they
# don't carry an environment (they are not scoped):
f <- quote(~foo)
f_env(f)

NULL

# By default unevaluated formulas are treated as formulas
is_formula(f)

[1] TRUE

# Supply `scoped = TRUE` to ensure you have an evaluated formula
is_formula(f, scoped = TRUE)

[1] FALSE

# By default unevaluated formulas not treated as bare formulas
is_bare_formula(f)

[1] FALSE

# If you supply `scoped = TRUE`, they will be considered bare
# formulas even though they don't inherit from `"formula"`
is_bare_formula(f, scoped = TRUE)

[1] FALSE

Examples for 'rlang::is_formula'

Is object a formula?