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From: Alan Brain <aebrain@dynamite.com.au>
Subject: Re: strongly typed langauge
Date: 1996/09/20
Message-ID: <3242665A.76FD@dynamite.com.au>#1/1
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Date: 1996-09-20T00:00:00+00:00
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AGBOH CHARLES wrote:

> Hi
 
> Could Some explain to me what the term "strongly typed language" is in the
> context of ada.  Could you give some examples and tips as on how to
> avoid errors related to this particular domain.

Geen Problem, Pas de Probleme

OK, this is best answered by an example.
Suppose you had a quantity of 5 apples and 11 oranges.

In an untyped language, you could add 07 and 0B (Hex) to make 10 (Hex)
In a weakly typed language, you could declare them both as Integer
quantities, and add 5 to 11 to get 16 - but 16 of what?
In a strongly typed language, unless you'd made a new type, FRUIT_TYPE,
and defined that apples and oranges were both subtypes of this base
type,
the compiler would reject a statement adding apples to oranges, as they
are two different types.

Similarly, suppose you knew that the number of apples had to be within
the range 0 to 47. A strongly typed language would allow you to express
this, as 

subtype NUMBER_OF_APPLES_TYPE is INTEGER range 0..47;

and any operation which resulted in a quantity >47 or <0 would cause a
failure to be detected. 

Tot Ziens/A Bientot 

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