Noob question: universal_integer type
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From: Duke Normandin on 21 May 2010 19:15 Coronado's Ada tutorial - Chapt3 [quote] The constant 17 is of a very special type defined by Ada as type "universal_integer" which can be combined with any of the integer types without specific conversion. [/quote] Let me get this right... if I use an undeclared integer in an expression, Ada will "deem it" to be a "universal_integer" and not choke at compile-time? -- Duke *** Tolerance becomes a crime, when applied to evil [Thomas Mann] ***
From: Yannick Duchêne (Hibou57) on 21 May 2010 19:33 Le Sat, 22 May 2010 01:15:19 +0200, Duke Normandin <dukeofperl(a)ml1.net> a écrit: > Coronado's Ada tutorial - Chapt3 > > [quote] > The constant 17 is of a very special type defined by Ada as type > "universal_integer" which can be combined with any of the integer types > without specific conversion. > [/quote] > > Let me get this right... if I use an undeclared integer in an expression, > Ada will "deem it" to be a "universal_integer" and not choke at > compile-time? On this subject, you may like to read a previous thread named âInteger questiaâ. Here is a Google Group link for conveniance: http://groups.google.com/group/comp.lang.ada/browse_thread/thread/d9d2bccce5d4fc93# The key, is that universal integer, is a type like other types you may defined. Every type integer-like type can be converted to and from universal integer. So, yes, the compiler will not complain, because if you have My_Constant : constant := 1; -- Named number, that is here, universal integer. type My_Integer_Type is range 1 .. 9; My_Entity : My_Integer_Type := My_Constant; the compiler will not see a contradiction, it will not see the declaration of a given type which is initialized with a value of a different type, it will see a literal, which it will automatically convert to the target type. -- There is even better than a pragma Assert: a SPARK --# check.
From: Yannick Duchêne (Hibou57) on 21 May 2010 19:34 Le Sat, 22 May 2010 01:33:02 +0200, Yannick Duchêne (Hibou57) <yannick_duchene(a)yahoo.fr> a écrit: > The key, is that universal integer, is a type like other types you may Sorry, a word is missing. Please, read âuniversal integer, is *not* a type like other typesâ. With apologizes. -- There is even better than a pragma Assert: a SPARK --# check.
From: Jeffrey R. Carter on 21 May 2010 19:37 Duke Normandin wrote: > > Let me get this right... if I use an undeclared integer in an expression, > Ada will "deem it" to be a "universal_integer" and not choke at > compile-time? I don't know, and I've been using Ada since 1984. What is "an undeclared integer"? 17 is an integer literal; all integer literals are universal_integer. 17 is not an undeclared integer. What the tutorial is trying to get across is that Ada, unlike some languages, does not have typed numeric literals (see also universal_real). You might encounter a language in which 10 is a literal of type int and 10L a literal of long int, for example. In Ada, all integer literals are universal_integer, and implicitly converted to specific integer types as required. Partly this makes life easier: you can change the type of a variable and not have to change all the literals used with that variable; and partly it's pretty much needed in a language that lets you define your own numeric types. -- Jeff Carter "C's solution to this [variable-sized array parameters] has real problems, and people who are complaining about safety definitely have a point." Dennis Ritchie 25
From: Duke Normandin on 21 May 2010 22:04
On 2010-05-21, Jeffrey R. Carter <spam.jrcarter.not(a)spam.acm.org> wrote: > Duke Normandin wrote: >> >> Let me get this right... if I use an undeclared integer in an expression, >> Ada will "deem it" to be a "universal_integer" and not choke at >> compile-time? > > I don't know, and I've been using Ada since 1984. What is "an undeclared integer"? > > 17 is an integer literal; all integer literals are universal_integer. 17 is not > an undeclared integer. > > What the tutorial is trying to get across is that Ada, unlike some languages, > does not have typed numeric literals (see also universal_real). You might > encounter a language in which 10 is a literal of type int and 10L a literal of > long int, for example. In Ada, all integer literals are universal_integer, and > implicitly converted to specific integer types as required. > > Partly this makes life easier: you can change the type of a variable and not > have to change all the literals used with that variable; and partly it's pretty > much needed in a language that lets you define your own numeric types. > OK! I got it... -- Duke *** Tolerance becomes a crime, when applied to evil [Thomas Mann] *** |