Question

In Specman I can convert a variable to a string using either:

x.to_string();

or

x.as_a(string);

Is there any difference between the two? If not, why does Specman provide both?

Answer 1

as_a() allows you to convert the expression to a specific type, not only string.

These are few examples from the docs

list_of_int.as_a(string)
list_of_byte.as_a(string)
string.as_a(list of int)
string.as_a(list of byte)
bool = string.as_a(bool) (Only TRUE and FALSE can be converted to Boolean; all other strings return an error)
string = bool.as_a(string)
enum = string.as_a(enum)
string = enum.as_a(string) 

UPDATE:

using as_a(string) and to_string() not always gives the same results.

var s: string;
s = "hello";
var lint: list of int;
lint = s.as_a(list of int);
print lint;
print lint.as_a(string);
print lint.to_string();

This will print something like this:

lint =
  104
  101
  108
  108
  111
lint.as_a(string) = "hello"
list.to_string() = "104 101 108 108 111"

This is because to_string will run on each element of the list and then the list will be concatenated with spaces, as_a will however convert integers to characters and concatenate them, giving you the hello word.