| Add Proposal | Add Analysis | Edit Class, Environment, or Release |
| Number | 411
|
| Category | enhancement
|
| Synopsis | extend operators to vectors and arrays
|
| State | open
|
| Class | enhancement
|
| Arrival-Date | Jul 31 2003
|
| Originator | Shalom Bresticker <Shalom.Bresticker@motorola.com>
|
| Release | 2001b
|
| Environment |
|
| Description |
This is a big subject and there are many possibilities. Each operator has to be considered separately. For example, a typical need is to do a bit-wise multiplexing operation. If I write a ? b[15:0] : c[15:0] it will just output b[15:0] or c[15:0]. Often what I want is: { a[15] ? b[15] : c[15], a[14] ? b[14] : c[14], a[13] ? b[13] : c[13], ... a[02] ? b[02] : c[02], a[01] ? b[01] : c[01], a[00] ? b[00] : c[00] } Yes, I can write (a[15:0] & b[15:0]) | (~a[15:0] & c[15:0]) but that's ugly. I would like to be able to apply unary operators to arrays also. And there are a lot of useful things to do with binary operators as well. -- Shalom Bresticker Shalom.Bresticker@motorola.com Design & Reuse Methodology Tel: +972 9 9522268 Motorola Semiconductor Israel, Ltd. Fax: +972 9 9522890 POB 2208, Herzlia 46120, ISRAEL Cell: +972 50 441478 |
| Fix |
|
| Audit-Trail |
From: Steven Sharp <sharp@cadence.com> To: etf-bugs@boyd.com, Shalom.Bresticker@motorola.com Cc: Subject: Re: enhancement/411: extend operators to vectors and arrays Date: Mon, 29 Sep 2003 17:35:12 -0400 (EDT) >For example, a typical need is to do a bit-wise multiplexing operation. > >If I write > >a ? b[15:0] : c[15:0] > >it will just output b[15:0] or c[15:0]. > >Often what I want is: > >{ >a[15] ? b[15] : c[15], >a[14] ? b[14] : c[14], >a[13] ? b[13] : c[13], >... >a[02] ? b[02] : c[02], >a[01] ? b[01] : c[01], >a[00] ? b[00] : c[00] } I have seen this come up in user designs also. >Yes, I can write > >(a[15:0] & b[15:0]) | (~a[15:0] & c[15:0]) > >but that's ugly. It also doesn't give quite the same results. If a[0] is X, and both b[0] and c[0] are 1, the conditional operator will correctly produce a 1 for the result. The boolean version will produce a more pessimistic result of X. Both versions will produce a 0 if both b[0] and c[0] are 0. If you change the boolean version to a product-of-sums instead of a sum-of-products representation, then it will get a 1 for both inputs 1, but will get X for both input 0. A bitwise conditional operator could get the less pessimistic answer in both cases. I am only aware of 2 other operators that are missing bitwise versions: case equality and case inequality. These can only produce a single bit result, not a vector of bits containing the results of comparing corresponding bits of the inputs. Note that logical equality and inequality do have bitwise versions: ~^ and ^ (XNOR and XOR). If vector operators were added for any of these, I don't know what would be a reasonable syntax. Steven Sharp sharp@cadence.com |
| Unformatted |
|
Hosted by Boyd Technology