RE: [sv-ec] RE: [sv-bc] SV-BC 291 is uploaded and ready

Hi Surrendra,

The behaviors you are describing have to do the greedy nature of bit
stream casting. I admit this may be an issue, but 291 has nothing to do
with it. And to address MarkH concerns, voting down 291 does not repeal
111, and neither changes the greedy nature of bit-stream casting. Away
to change this would be to say that casting to an equivalent type was
not greedy, but instead preserved the dynamic sizes.

Also, a bit-stream cast, or any cast for that matter, is just an
expression. The type or the contents of the LHS of an assignment have no
effect on the cast. I don't think the previous contents of the LHS have
any effect on any assignment. (Except in determining whether an element
an associative array already exists). See more comments below

________________________________

From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf Of
Surrendra Dudani
Sent: Tuesday, November 16, 2004 6:33 PM
To: sv-bc@eda.org; sv-ec@eda.org
Subject: Re: [sv-ec] RE: [sv-bc] SV-BC 291 is uploaded and ready

Hi Dave,
I apologize for making a typo in the example. It should have been
a = dest_t'(b); (1)

Since the rules of unpacked structure assignment are not clearly stated,
let me give some examples of unpacked array assignment with string as
the type of the element. The elements of the lhs and rhs arrays are of
equivalent type, but of different lengths.

typedef string source_t[2];
typedef source_t dest_t;

source_t a;
dest_t b;

a[0] = "ab";
a[1] = "c";
b[0] = "defg";
b[1] = "hijk";

b = dest_t'(a); (1)
b = a; (2)
(1) is illegal, as the lhs bit length is different than rhs bit length

This is legal. b[0] = "abc"; b[1]="";
(2) is legal, since each element is equivalent and the array lengths are
equal

Yes. b[0] and b[1] will be resized.

And, in the simple case

string s1 = "ab";
string s2 = "cde"
s1 = s2; (3)
s1 = string'(s2); (4)
(3) is legal, but, would (4) produce a run time error?

(3) and (4) are both legal. The previous size of s1 is irrelevant.

And, in a more complicated case,

typedef string source_t1[2];
typedef string dest_t1[];

source_t1 a1;
dest_t1 b1 = new[2];

a1[0] = "ab";
a1[1] = "c";
b1[0] = "defg";
b1[1] = "hijk";

b1 = dest_t1'(a1); (1)
b1 = a1; (2)
(1) is illegal, as the lhs bit length is different than rhs bit length

I think this case, a nested dynamic type, is undefined in the LRM. I
would be OK with making this type of cast illegal. But I would also be
OK with

b1[0] ="abc";.

(2) is legal, since each element is equivalent and the array lengths are
equal

I agree.

Surrendra
Received on Tue Nov 16 16:05:35 2004