SDL-News: casting to parent type ?

Subject: SDL-News: casting to parent type ?
From: Thomas Garsiot (
Date: Fri Dec 08 2000 - 08:46:26 GMT

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Is there any way of casting a variable to its parent type ?

This is what I'm trying to do :

there is a built-in Octet_String type with a substring axiom (coming
from ASN-1 String0 generator).

This is a type we created :

newtype Frame inherits Octet_String operators all;
    adding operators ...
endnewtype Frame;

I want to extract data from a frame using :
Data := substring(sdu,24,48) where Data is an Octet_String and sdu a
Frame (for example)

if sdu is of type Frame, I get (using Telelogic Tau SDL-Suite):

Type mismatch for variable, formal_parameter, literal or synonym.
Data := substring(?sdu,24,48)

if I try to cast sdu to Octet_String (Data:=<<Type Octet_String>>
substring(sdu,24,48)) I get the same error message.

What I'd like to do is something like

Does anybody know the SDL equivalent for this ?

Thanks in advance.



--End text from Thomas Garsiot <> to sdlnews ---
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