Re: [sv-bc] structure literal example in standard

Bresticker, Shalom wrote:

> Krinshanu Debnath wrote:

>>obj = '{a, '{2{b,c}}};
>>
>>Now if I want to assign value in 1D array obj1, I would extend
>>it to ..
>>
>>obj1 = '{3{'{a, '{2{b,c}}}}};
> 
> Here, you want to do 
> 
> obj1 = '{3{obj}} ;
> 
> But if you substitute the structure literal for obj, then you omit the
> leading '. You can think of it as moving to precede the {3.

Not so.  There are no such magic rules about how replication works.

The example on page 12 is wrong, and its expansion has been bungled.
Here is a corrected version:

struct {int X,Y,Z;} XYZ = '{3{1}};
typedef struct {int a,b[4];} ab_t;
int a,b,c;
ab_t v1[1:0] [2:0];
v1 = '{2{'{3{'{a,'{2{b,c}}}}}}};
/* expands to '{ '{3{ '{ a, '{2{ b, c }} } }},
                  '{3{ '{ a, '{2{ b, c }} } }}
                } */

/* expands to '{ '{ '{ a, '{2{ b, c }} },
                     '{ a, '{2{ b, c }} },
                     '{ a, '{2{ b, c }} }
                   },
                  '{ '{ a, '{2{ b, c }} },
                     '{ a, '{2{ b, c }} },
                     '{ a, '{2{ b, c }} }
                   }
                } */

/* expands to '{ '{ '{ a, '{ b, c, b, c } },
                     '{ a, '{ b, c, b, c } },
                     '{ a, '{ b, c, b, c } }
                   },
                  '{ '{ a, '{ b, c, b, c } },
                     '{ a, '{ b, c, b, c } },
                     '{ a, '{ b, c, b, c } }
                   }
                } */

Since there is enough room on the page, please use the vertical
pattern to better illustrate the repetitive behavior.

Greg Jaxon

> 
> In the following case:
> 
> 
>>int n[1:2][1:3] = '{2{3{y}}}}
> 
> 
> you chain the replications, so you need the ' between them.
> 
> Similarly, 
> 
> 
>>int a[4] = '{b, b, 2{b}};
> 
> 
> Here also, each replication requires ' before it.
> So you need
> 
> 
>>int a[4] = '{b, b, '{2{b}}};
> 
> 
> Shalom
> 
> 
> 
>>-----Original Message-----
>>From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On
>>Behalf Of Krishanu Debnath
>>Sent: Thursday, January 05, 2006 1:46 PM
>>To: sv-bc@eda.org
>>Subject: Re: [sv-bc] structure literal example in standard
>>
>>Shalom, I don't think I understand your point. Let me allow to
>>elaborate this
>>example.
>>
>></code_begin>
>>
>>struct {int X,Y,Z;} XYZ = '{3{1}};
>>typedef struct {int a,b[4];} ab_t;
>>int a,b,c;
>>
>>ab_t obj;
>>ab_t obj1 [2:0];
>>ab_t obj2 [1:0][2:0];
>>
>></code_end>
>>
>>Now if I want to assign value in obj.b array, I would write
>>following array
>>literal.
>>
>>obj.b = '{2{b,c}} // It should be okay because replication
>>represents the
>>                   // whole dimension [*]
>>
>>Now if I want to assign value in obj struct, I would extend it
>>to ..
>>
>>obj = '{a, '{2{b,c}}};
>>
>>Now if I want to assign value in 1D array obj1, I would extend
>>it to ..
>>
>>obj1 = '{3{'{a, '{2{b,c}}}}};
>>
>>So if we think obj2 is a 1D array of element obj1 of length 2.
>>
>>obj2 = '{2{'{3{'{a, '{2{b,c}}}}}}};
>>
>>Now does it match with the example shown in standard?
>>
>>
>>Bresticker, Shalom wrote:
>>
>>>No.
>>>
>>>You can see it described in 8.13.1, paragraph 2:
>>>
>>>A syntax resembling multiple concatenations can be used in
>>
>>array
>>
>>>assignment patterns as well. Each replication
>>>represents a single dimension.
>>>
>>>unpackedbits = '{2 {y}} ; // same as '{y, y}
>>>int n[1:2][1:3] = '{2{'{3{y}}}}; // same
>>
>>as'{'{y,y,y},'{y,y,y}}
>>
>>Yes perfectly valid example. But does the verse of 8.13.1p2
>>allow you to omit
>>the 'apostrophe' when you are replicating the value for most
>>varying dimension?
>>If so then
>>int n[1:2][1:3] = '{2{3{y}}}} is valid?
>>
>>
>>Krishanu
>>
>>[*] Sec 8.13.1p2 says ..
>>"A syntax resembling multiple concatenations can be used in
>>array assignment
>>  patterns as well. Each replication represents a single
>>dimension."
>>
>>Does it also implies that you need to specify all the elements
>>of that
>>dimension, if you are using replication operator?
>>
>>e.g
>>
>>int b;
>>int a[4] = '{4{b}}; // valid
>>
>>but ,
>>
>>int a[4] = '{b, b, 2{b}}; // is valid?
>>
>>FYI, most of the tools reject the second initialization.
>>
>>
>>>==
>>>
>>>You can also see it in assignment_pattern syntax (Syntax 8-
>>
>>2):
>>
>>>assignment_pattern ::=
>>>  '{ expression { , expression } }
>>>...
>>>| '{ constant_expression { expression { , expression } } }
>>>
>>>
>>>Shalom
>>>
>>>
>>>>-----Original Message-----
>>>>From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On
>>>>Behalf Of Krishanu Debnath
>>>>Sent: Thursday, January 05, 2006 12:16 PM
>>>>To: sv-bc@eda.org
>>>>Subject: [sv-bc] structure literal example in standard
>>>>
>>>>Hello,
>>>>
>>>>I am not sure about the correctness of the following
>>
>>example,
>>
>>>>taken from
>>>>Sec 3.8 _Structure literals_.
>>>>
>>>>struct {int X,Y,Z;} XYZ = '{3{1}};
>>>>typedef struct {int a,b[4];} ab_t;
>>>>int a,b,c;
>>>>ab_t v1[1:0] [2:0];
>>>>v1 = '{2{'{3{a,'{2{b,c}}}}}};
>>>>/* expands to '{'{3{'{a,{2{b,c}}}}}, '{3{{a,'{2{b,c}}}}}} */
>>>><rest snipped>
>>>>
>>>>Here the array literal assign to v1 is incorrect. I think
>>>>example
>>>>missed the "'" after struct literal. So it should be
>>>>'{2{'{3{'{a,'{2{b,c}}}}}}}. Similarly example missed the "'"
>>
>>in
>>
>>>>second element of expansion.
>>>>
>>>>Can anyone please confirm?
>>>>
>>>>Thanks,
>>>>Krishanu
>>>>
> 
>