f_capture: Make a promise explicit by converting into a formula.
In lazyeval: Lazy (Non-Standard) Evaluation

Description Usage Arguments Value Examples

This should be used sparingly if you want to implement true non-standard evaluation with 100% magic. I recommend avoiding this unless you have strong reasons otherwise since requiring arguments to be formulas only adds one extra character to the inputs, and otherwise makes life much much simpler.

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f_capture(x)

dots_capture(..., .ignore_empty = TRUE)

`x, ...`	An unevaluated promises
`.ignore_empty`	If `TRUE`, empty arguments will be silently dropped.

f_capture returns a formula; dots_capture returns a list of formulas.

f_capture(a + b)
dots_capture(a + b, c + d, e + f)

# These functions will follow a chain of promises back to the
# original definition
f <- function(x) g(x)
g <- function(y) h(y)
h <- function(z) f_capture(z)
f(a + b + c)