do.call test

# see ?do.call

# The second argument in do.call are evaluated in the calling environmnet before passing to Internal function.
# If an original function requires its arguments as expression, language, or call objects,
# they are needed to be quoted, or set do.call option as quote = TRUE.

D(quote(x^5), "x") # works

do.call(D, list(quote(x^5), "x")) # not work
do.call(D, list(quote(x^5), "x"), quote = TRUE) # works 
do.call(D, list(quote(quote(x^5)), "x")) # works

eval(call("D", quote(x^5), "x")) # not work
eval(call("D", quote(quote(x^5)), "x")) # works

eval(as.call(list(D, quote(x^5), "x"))) # not work
eval(as.call(list(D, quote(quote(x^5)), "x"))) # works

### environment's effect
myenv <- new.env(parent = emptyenv())
assign("g", function(x) x^2, myenv)
assign("val", 10, myenv)

g <- function(x) x / 2
val <- 9

do.call(g, list(val), envir = myenv) # 4.5
do.call("g", list(val), envir = myenv) # 81
do.call(g, list(quote(val)), envir = myenv) # 5
do.call("g", list(quote(val)), envir = myenv) # 100

(function(fun, env){
  print(do.call(g, list(val), envir = env)) # 4.5
  print(do.call("g", list(val), envir = env)) # 81
  print(do.call(g, list(quote(val)), envir = env)) # 5
  print(do.call("g", list(quote(val)), envir = env)) # 100
  
  print(do.call(fun, list(val), envir = env)) # 4.5
  print(do.call(as.character(substitute(fun)), list(val), envir = env)) # 81
  print(do.call(fun, list(quote(val)), envir = env)) # 5
  print(do.call(as.character(substitute(fun)), list(quote(val)), envir = env)) # 100
})(g, myenv)

eval(call("g", val)) # 4.5
eval(call("g", quote(val))) # 4.5
eval(call("g", val), envir = env) # 81
eval(call("g", quote(val)), envir = env) # 100
eval(quote(g(val))) # 4.5
eval(quote(g(val)), envir = env) # 100