Pipe dispatch implementation.

This is a helper for implementing additional pipes.

pipe_impl(pipe_left_arg, pipe_right_arg, pipe_environment, pipe_string = NULL)

Arguments

pipe_left_arg	possibily unevaluated left argument.
pipe_right_arg	possibly unevaluated right argument.
pipe_environment	environment to evaluate in.
pipe_string	character, name of pipe operator.

Value

result

Examples

# Example: how wrapr pipe is implemented

print(`%.>%`)
#> function (pipe_left_arg, pipe_right_arg) 
#> {
#>     pipe_left_arg <- substitute(pipe_left_arg)
#>     pipe_right_arg <- substitute(pipe_right_arg)
#>     pipe_environment <- parent.frame()
#>     pipe_string <- as.character(sys.call()[[1]])
#>     pipe_impl(pipe_left_arg, pipe_right_arg, pipe_environment, 
#>         pipe_string)
#> }
#> <bytecode: 0x7fc757e03ca0>
#> <environment: namespace:wrapr>




# Example: create a value that causes pipelines to record steps.

# inject raw values into wrapped/annotated world
unit_recording <- function(x, recording = paste(as.expression(substitute(x)), collapse = '\n')) {
  res <- list(value = x, recording = recording)
  class(res) <- "recording_value"
  res
}

# similar to bind or >>=
# (takes U, f:U -> V to M(f(U)), instead of
#        U, f:U -> M(V) to M(f(U)))
# so similar to a functor taking
#   f:U -> V to f':M(U) -> M(V)
# followed by application.
apply_left.recording_value <- function(
  pipe_left_arg,
  pipe_right_arg,
  pipe_environment,
  left_arg_name,
  pipe_string,
  right_arg_name) {
  force(pipe_environment)
  tmp <- wrapr::pipe_impl(
    pipe_left_arg = pipe_left_arg$value,
    pipe_right_arg = pipe_right_arg,
    pipe_environment = pipe_environment,
    pipe_string = pipe_string)
  unit_recording(
    tmp,
    paste0(pipe_left_arg$recording,
           ' %.>% ',
           paste(as.expression(pipe_right_arg), collapse = '\n')))
}

# make available on standard S3 search path
assign('apply_left.recording_value',
       apply_left.recording_value,
       envir = .GlobalEnv)

unpack[value, recording] := 3 %.>%
  unit_recording(.) %.>%
  sin(.) %.>%
  cos(.)

print(value)
#> [1] 0.9900591
print(recording)
#> [1] ". %.>% sin(.) %.>% cos(.)"

# clean up
rm(envir = .GlobalEnv, list = 'apply_left.recording_value')