parents : (string -> string list)

SYNOPSIS
Lists the parent theories of a named theory.

DESCRIBE
The function parents returns a list of strings that identify the parent theories of a named theory. The function does not recursively descend the theory hierarchy in search of the `leaf' theories. The named theory must be the current theory or an ancestor of the current theory.

FAILURE
Fails if the named theory is not an ancestor of the current theory.

EXAMPLE
Initially, the only parent is the main HOL theory:
   #new_theory `my-theory`;;
   () : void

   #parents `my-theory`;;
   [`HOL`] : string list

   #parents `HOL`;;
   [`tydefs`; `sum`; `one`; `BASIC-HOL`] : string list

   #parents `tydefs`;;
   [`ltree`; `BASIC-HOL`] : string list

   #parents `string`;;
   evaluation failed     parents -- string is not an ancestor
However, loading the string library creates several additional ancestor theories:
   #load_library `string`;;
   Loading library `string` ...
   Updating search path
   .Updating help search path
   .Declaring theory string a new parent
   Theory string loaded
   ......
   Library `string` loaded.
   () : void

   #parents `string`;;
   [`ascii`; `HOL`] : string list

   #parents `my-theory`;;
   [`string`; `HOL`] : string list

SEEALSO  ancestors,   ancestry

HOL  Kananaskis 0