Section 12.2

LRM-287

Change (changes in red and blue)

// EXAMPLE 1: restrict to small low addresses

res = bus.randomize()with {atype == small low;};

LRM-287

Change (changes in red and blue)

class MyYXPair MyXYPair extends XYPair ;

Section 12.4

LRM-288

Change in Syntax 12-2 (changes in red and blue)

constraint_declaration ::= [ static ] constraint constraint_identifier { { constraint_block } } // from Annex A.1.9

constraint_block ::= { { constraint_block_item } }

constraint_block_item ::=

solve identifier_list before identifier_list ;

| constraint_expression

constraint_expression ::=

expression_or_dist ;

| expression –> constraint_set

| if ( expression ) constraint_set [ else constraint_set ]

| expression dist { dist_list } ;

| foreach ( array_identifier [ loop_variables ] ) constraint_set

LRM-287

Change in Syntax 12-2 (changes in red and blue)

dist_item ::=

value_range := expression

| value_range :/ expression

dist_item ::= value_range [ dist_weight ]

dist_weight ::=

:= expression

| :/ expression

LRM-288

Change in Syntax 12-2 (changes in red and blue)

constraint_prototype ::= [ static ] constraint constraint_identifier ;

extern_constraint_declaration ::=

[ static ] constraint class_identifier :: class_scope constraint_identifier { { constraint_block } }

LRM-288

Change in Syntax 12-2 (changes in red and blue)

identifier_list ::= identifier { , identifier }

expression_or_dist ::= expression [ dist { dist_list } ] // from Annex A.1.9

Section 12.4.4

LRM-288

Change in Syntax 12-3 (changes in red and blue)

constraint_block ::= // from Annex A.1.9

...

| expression dist { dist_list } ;

dist_list ::= dist_item { , dist_item } // from Annex A.1.9

dist_item ::= value_range [ dist_weight ]

dist_weight ::=

:= expression

| :/ expression

expression_or_dist ::= expression [ dist { dist_list } ] // from Annex A.1.9

Section 12.4.5

LRM-287

Change (changes in red and blue)

Constraints provide two constructs for declaring conditional (predicated) relations: implication implication and if...else.

Section 12.4.9

LRM-288

Change in Syntax 12-7 (changes in red and blue)

constraint_block_item ::=

solve identifier_list before identifier_list ;

| constraint_expression

LRM-305

Change (changes in red and blue)

The constraint c says “s implies d equals zero”. Although this reads as if s determines d, in fact s and d are determined together. There are 2³² 2³³ valid possible combinations of {s,d}, but s is only true for {1,0}. Thus, the probability that s is true is 1/2³² 1/2³³, which is practically zero.

Section 12.4.10

LRM-288

Change in Syntax 12-8 (changes in red and blue)

constraint_declaration ::= // from Annex A.1.9

[ static ] constraint constraint_identifier { { constraint_block } }

Section 12.4.11

LRM-287

Change (changes in red and blue)

constraint C1 { length == count_ones( v ) ; };

LRM-288

Change (changes in red and blue)

constraint C2

{

length == ((wv>>9)&1) + ((wv>>8)&1) + ((wv>>7)&1) + ((wv>>6)&1) + ((wv>>5)&1) +

((wv>>4)&1) + ((wv>>3)&1) + ((wv>>2)&1) + ((wv>>1)&1) + ((wv>>0)&1);

}

Unlike the count_ones function, more complex properties, which require temporary state or unbounded loops, may be impossible to convert into a single expression. The ability to call functions, thus, enhances the expressive power of the constraint language and reduces the likelihood of errors. Note that the two constraints above are not completely equivalent; C2 is bidirectional (length length can constrain wv and vice-versa), whereas C1 is not.

LRM-287

Change (changes in red and blue)

class B;

rand int x, y;

constraint C { x <= F(y); };

constraint D { y inside { 2, 4, 8 }; };

endclass

Section 12.6

LRM-288

Change in Syntax 12-9 (changes in red and blue)

inline_constraint _declaration ::= // not in Annex A

class_variable_identifier . randomize [ ( [ variable_identifier_list | null ] ) ]

with { { constraint_block } }

Section 12.11

LRM-288

Change in Syntax 12-10 (changes in red and blue)

scope_randomize ::= // not in Annex A

[ std:: ] randomize ( [ variable_identifier_list ] ) [ with { { constraint_block } } ]