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Concatenate expressions via a binary operator

Source: R/utils.R
call_concatenate.Rd

e.g. combine with + for ggplot without introducing parentheses due to associativity

Usage 

call_concatenate(args, bin_op = "+")

Arguments

args

arguments to concatenate with operator

bin_op

binary operator to concatenate it with

Value

a call

Examples 

library(ggplot2)

# What we want to achieve
call("+", quote(f), quote(g))
#> f + g
call("+", quote(f), call("+", quote(g), quote(h))) # parentheses not wanted
#> f + (g + h)
call("+", call("+", quote(f), quote(g)), quote(h)) # as expected without unnecessary parentheses
#> f + g + h
Reduce(function(existing, new) call("+", existing, new), list(quote(f), quote(g), quote(h)))
#> f + g + h

# how we do it
call_concatenate(list(quote(f), quote(g), quote(h)))
#> f + g + h
call_concatenate(list(quote(f)))
#> f
call_concatenate(list())
#> NULL
call_concatenate(
  list(quote(ggplot(mtcars)), quote(geom_point(aes(wt, mpg))))
)
#> ggplot(mtcars) + geom_point(aes(wt, mpg))

eval(
  call_concatenate(
    list(quote(ggplot(mtcars)), quote(geom_point(aes(wt, mpg))))
  )
)