Re: [sv-ec][URGENT] email ballot #4, on Erratum 275, voting closes on 15 Dec 2004

Bill,

The reason why "str.putc(i, "AB");" is legal, has nothing to do with
putc. It is the natural way in which Verilog truncates string-literals and
integral values that are copied onto smaller size variables.

Note that:
        str.putc( i, "AB" );
behaves in the same way as:
        byte c = "AB";
        str.putc( i, c );

Likewise, the reason why "str.putc(i, x);" -- where x is a string ---, is illegal,
has nothing to do with putc. Currently, strings cannot be assigned directly
to a byte (or any other integral value). If the rules allowed for direct assignment
of strings to integral values then "str.putc(i, x);" would naturally be allowed.
Note how the same applies to:
    string x = "A";
    byte c = x; // not OK
    byte c =byte`(x); // OK

Perhaps you'd like to propose an enhancement that relaxes the type checking
for string variables? That would be completely orthogonal to this proposal.

Also, I'm not sure I understand what you mean by :
    putc should be removed, since it has no simple "semantic equivalent".

Putc does have a semantic equivalent: assignment with an indexed string
on the left-hand-side. In fact, the two are exactly the same semantically.
putc provides an object-oriented syntax, and assignment provides an operator
syntax.

Part of the purpose of this proposal was to make the two consistent.

    Arturo

----- Original Message -----
From: "William Paulsen" <paulsen@cadence.com>
To: "Arturo Salz" <Arturo.Salz@synopsys.COM>; <sv-ec@eda.org>
Sent: Thursday, December 09, 2004 11:18 AM
Subject: RE: [sv-ec][URGENT] email ballot #4, on Erratum 275, voting closes on 15 Dec 2004

> Arturo,
>
> Thanks for your comments - I still find it unfortunate that these are
> legal:
>
> str.putc(i, "A"); => OK, assigns "A" to str[i]
> str.putc(i, "AB"); => OK, assigns "B" to str[i]
>
>
> But this is illegal:
>
> string x = "A";
> str.putc(i, x); => Not allowed. Use str.putc(i, x[0]);
>
>
>
> I think putc should be removed, since it has no simple "semantic
> equivalent".
>
> Bill
>
>
>
>
> > -----Original Message-----
> > From: Arturo Salz [mailto:Arturo.Salz@synopsys.com]
> > Sent: Thursday, December 09, 2004 1:29 PM
> > To: William Paulsen; sv-ec@eda.org
> > Subject: Re: [sv-ec][URGENT] email ballot #4, on Erratum 275,
> > voting closes on 15 Dec 2004
> >
> > Bill,
> >
> > Just a few comments on your vote, interspersed below.
> >
> > Arturo
> >
> > ----- Original Message -----
> > From: "William Paulsen" <paulsen@cadence.com>
> > To: "Mehdi Mohtashemi" <Mehdi.Mohtashemi@synopsys.COM>;
> > <sv-ec@eda.org>
> > Sent: Thursday, December 09, 2004 8:05 AM
> > Subject: RE: [sv-ec][URGENT] email ballot #4, on Erratum 275,
> > voting closes on 15 Dec 2004
> >
> >
> > > Mehdi,
> > >
> > > Three No votes with comments, and one Yes.
> > >
> > > Bill
> > >
> > >
> > > >
> > > > ===============Erratum 275, =========
> > > >
> > > > Please respond to the items in this erratum, place an X in
> > > > the appropriate box and place explanation for No vote.
> > > >
> > > > Errata 275 (proposal uploaded 12/8/2004, also attached)
> > > > item 1. The type of a single character within a string is byte
> > > > ____ Yes __X__ No
> > > >
> > >
> > > A single character should be a "byte unsigned" not just
> > "byte", which is
> > > signed.
> > >
> >
> > The type of a string character was already a byte
> > (certainly for reading),
> > thisproposal doesn't change that. Theonly thing this
> > proposal does is
> > generalize the type of a string character for both
> > reading and writing.
> > Whether the character should be unsigned or not is a
> > separate issue
> > that is not part of this vote.
> >
> > > Also, I don't like this sentence from Section 3.7, at the end of
> > > paragraph 4:
> > > "A string shall not contain the special character "\0".
> > >
> > > People using strings will expect similar behavior as in C,
> > for example
> > > they might want to shorten a string by explicitly putting a 0 in the
> > > middle of a string.
> > >
> >
> > That particluar paragraph is not part of this proposal.
> > That sentence
> > is part of the previously approved erratum 334.
> >
> > Note tat SV strings are not C strings. They are dynamic
> > objects whose
> > length exactly matches the contents of the string.
> > Truncating a string
> > by writing a 0-byte in the middle of the string would
> > requires either that
> > the string contents be reallocated to match the new size
> > or leak memory.
> > This is very different from C strings. Bythe way, users
> > can still get the
> > same behavior as in C by using a byte array and
> > manipulating the 0-byte
> > terminators explicitly as done in C.
> >
> > >
> > >
> > > > item 2: The putc method has only one prototype: task
> > putc(int i,
> > > byte c );
> > > > ____ Yes _X___ No
> > >
> > > I think the blue text is confusing: It says that if the
> > second argument
> > > is an "empty string" then the variable is unaffected.
> > >
> > > But "unaffected" means that the Note about being
> > semantically equivalent
> > > to an assignment is confusing and incorrect - this note should be
> > > removed. But it could be replaced with equivalent code
> > that does the
> > > checking for 0-length and 0-valued strings.
> > >
> >
> > Since strings cannot contain 0-valued bytes (arratum 334)
> > then attempting
> > to assign a 0-byte to a character in the middle of the
> > string should not be
> > able to change the value of an embedded character to 0.
> > Therefore, the "Note" part can be removed and made mandatory.
> >
> > > Also, this proposal should have examples that state if these common
> > > usages are legal or illegal:
> > >
> > > str.putc(i, "A");
> > > str.putc(i, "AB");
> > >
> > > string x = "A";
> > > str.putc(i, x);
> > >
> > >
> >
> > These are all governed by the conversion rules to a byte.
> > str.putc(i, "A"); => OK, assigns "A" to str[i]
> > str.putc(i, "AB"); => OK, assigns "B" to str[i]
> > str.putc(i, x); => Not allowed. Use
> > str.putc(i, x[0]);
> >
> > >
> > > >
> > > > item 5: Typo in example, example should be modified
> > > > ____ Yes _X___ No
> > >
> > > The example should include this:
> > >
> > > string x = "A";
> > > str[j] = x; // OK or not OK?
> > >
> >
> > An example might be useful, but the answer is clear.
> > The type of a string character is byte, thus, str[j] is a byte,
> > and assigning a string to an integral type without a cast is
> > not allowed (erratum 271). Therefore, the example is an error.
> > >
> > > >
> > > > item 8: Usage of word string: Create a new erratum
> > > > for this, and close 275 if all items above
> > > pass
> > > > _X___ Yes ____ No
> > > >
> > > > ================================================================
> > > >
> > > >
> > > >
> > >
> >
> >
> >
>
Received on Thu Dec 9 12:11:18 2004