* Re: 'Base and Staticness
[not found] <12293281394.11.MENDAL@Sierra.Stanford.EDU>
@ 1987-04-13 13:45 ` arny
1987-04-14 8:48 ` deller
0 siblings, 1 reply; 2+ messages in thread
From: arny @ 1987-04-13 13:45 UTC (permalink / raw)
In article <12293281394.11.MENDAL@Sierra.Stanford.EDU>, Mendal@SIERRA.STANFORD.EDU (Geoff Mendal) writes:
> Is the following package specification semantically valid?
>
> package Static_Test is
> subtype Non_Static is Integer range Integer (1) .. 100;
>
> type Must_Be_Static is range Non_Static'Base'First .. 10;
> end Static_Test;
>
> Read the ARM, 3.3.3(8..9) and 4.9(1..2, 8, 11).
Forgive me if I missed something, but after checking the LRM sections you
mentioned above (especially 4.9:11), I believe the subtype "Non_Static" is
indeed static. This subtype is formed by imposing a static range constraint
(1..100) on a scalar base type (Integer). (Note that enclosing the numeral 1
in parentheses does not make it non-static according to 4.9:2,4,10).
It follows that the declaration of "Must_Be_Static" is then valid according
to 4.9:8.
Comments?
Arny B. Engelson {ihnp4|bonnie|clyde}!wayback!arny (201) 386-4816
AT&T Bell Laboratories, Whippany, N.J.
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: 'Base and Staticness
1987-04-13 13:45 ` 'Base and Staticness arny
@ 1987-04-14 8:48 ` deller
0 siblings, 0 replies; 2+ messages in thread
From: deller @ 1987-04-14 8:48 UTC (permalink / raw)
In article <1132@wayback.UUCP>, arny@wayback.UUCP (Arny B. Engelson) writes:
> > Is the following package specification semantically valid?
> > package Static_Test is
> > subtype Non_Static is Integer range Integer (1) .. 100;
> > type Must_Be_Static is range Non_Static'Base'First .. 10;
> > end Static_Test;
> > Read the ARM, 3.3.3(8..9) and 4.9(1..2, 8, 11).
>
> ... I believe the subtype "Non_Static" is
> indeed static. This subtype is formed by imposing a static range constraint
> (1..100) on a scalar base type (Integer). (Note that enclosing the numeral 1
> in parentheses does not make it non-static according to 4.9:2,4,10).
> . . .
I believe you missed the fact that instead of "1", the expression is
"Integer (1)", not simply "(1)". "Integer (1)" is a type conversion, which is
not listed in RM 4.9 as a static primary. Using a "non-modifying" type
conversion is one of the typical "tricks" used to make expressions non-static.
Note that "Integer'(1)" is a qualified expression, which _is_ a static
expression primitive, and is more likely to be used when "casting" (What, how
did C sneak in here?) a literal to a specific type.
Steven Deller,
Verdix
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{verdix,seismo,umcp-cs}!vrdxhq!deller
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