Defines functions wrap_function

# Wrap an expression in a function
# This function takes the "body" part of a function and wraps it in
# a function. The return value depends on whether the function is created
# for its side effect with the tee operator. If the operator is \code{\%$\%}
# then the expression will be evaluated in a \code{with(., )} statement.
# @param body an expression which will serve as function body in single-argument
#    function with an argument names \code{.} (a dot)
# @param pipe a quoted magrittr pipe, which determines how the function is made.
# @param env The environment in which to contruct the function.

# @details Currently, the only distinction made is whether the pipe is a tee
#   or not.
# @return a function of a single argument, named \code{.}.
wrap_function <- function(body, pipe, env)
  if (is_tee(pipe)) {
    body <- call("{", body, quote(.))
  } else if (is_dollar(pipe)) {
    body <- substitute(with(., b), list(b = body))
  eval(call("function", as.pairlist(alist(.=)), body), env, env)

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magrittr documentation built on May 29, 2017, 12:37 p.m.