simple parameter checking

param-must-be.R

`%must_be%` <- function(x, value) {
  pr <- parent.frame()
  var_must_be(x, value, .call = match.call())
}

var_must_be <- function(x, value, .call = NULL) {
  mc <- if (is.null(.call)) match.call() else .call
  
  # maybe must_be_like?  where class(value) is in class(x) etc?
  ok <- 
    identical(class(x), class(value)) &
    identical(typeof(x), typeof(value)) &
    identical(length(x), length(value))
  
  if (!ok) {
    print(mc)
    msg <- sprintf("%s is not %s", deparse(as.list(mc)$x), deparse(as.list(mc)$value))
    stop(argsError(msg))
  }
  
  invisible()
}

argsError <- function(msg, call = NULL) {
  cl <- c("argsError", "simpleError", "error", "condition")
  structure(list(message = msg, call = call), class = cl)
}

foo <- 1:3
try(foo %must_be% integer(4))

c(1, 3, 2) %must_be% double(3)
try(c(1, 3, 2) %must_be% double(2))