From: James A. Markevitch (jam@magic.com)
Date: Sun Jan 23 2000 - 11:06:28 PST
More comments on Draft 4 BNF.
Section A.2.3
list_of_local_param_assignments is defined in this section, but is not
used anywhere. The local_parameter_declaration in section A.2.1.1
uses list_of_param assignments.
Section A.6.3
Should function_seq_block have an optional attribute_instance? seq_block
has this, but function_seq_block does not.
Section A.8.4
genvar_primary does not contain "( mintypmax_expression )" or anything
analogous to that. I think this is the right thing, since it is closer
to a constant_primary, rather than a normal primary. Is this definitely
correct?
Sections A.7.3 and A.9.3
input_identifier and output_identifier are defined in two places. I believe
that they should be left in section A.7.3 and removed from section a.9.3.
Section A.2.2.3
delay_value includes mintypmax_expression. Should this be
constant_mintypmax_expression? In 1995 it used the constant version.
<p><p>Constant functions for delays
If a delay_value is allowed to include any constant_mintypmax_expression,
including a constant_function_call, then this creates a tough situation for
parsers. For example,
udpname #f(a,b) (c,d);
When parsing this, the parser doesn't know, until the second open paren
is encountered, whether or not "(a,b)" is the udp_instance or a list of
arguments to function "f". Since section 10.3.5 does not appear to require
that constant functions be declared before they are used, the parser cannot
even get a hint that "f" is a function. Thus, it must scan until it sees
the second open paren, then make the decision about how to interpret "(a,b)".
Note that such hard-to-parse constructs are not new to Verilog. In 1995,
in the following:
mod_or_udp #(2) inst_name(a, b, c);
"#(2)" can be either a delay value or a parameter override and cannot be
resolved until elaboration time when it is known whether "mod_or_udp" is a
module or a UDP.
Comments?
<p><p>General comment
Need to add "constant functions" to the index.
James Markevitch
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