///assert(expr, msg)
/**
 * assert :: Boolean -> a[a->String] -> ()
 * 
 * Asserts an expression is true. If not, the program halts with the given message.
 *
 * @param expr the expression to test
 * @param msg the message shown if the assertion fails
 */

if (!argument0)
  show_error(string(argument1), true);