Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision 		Previous revision
language:connections [2019/04/18 14:14]
rajit [User-defined Type Connections] 		language:connections [2023/04/09 19:13] (current)
rajit [Assertions]
Line 14: Line 14:
 variables of type ''bool''. variables of type ''bool''.
  
-<code>+<code act>
 bool x, y; bool x, y;
 x=y; x=y;
Line 27: Line 27:
 parameters. parameters.
  
-<code>+<code act>
 pint x, y; pint x, y;
 x=5; x=5;
Line 36: Line 36:
 meta-language variables is not symmetric, as illustrated below. meta-language variables is not symmetric, as illustrated below.
  
-<code>+<code act>
 pint x, y; pint x, y;
 x=5; x=5;
 x=y*1+2; x=y*1+2;
 +</code>
 +<code>
 -[ERROR]-> id: y -[ERROR]-> id: y
            FATAL: Uninitialized identifier            FATAL: Uninitialized identifier
Line 49: Line 51:
 meta-language variable assignments. meta-language variable assignments.
  
-<code>+<code act>
 pint x; pint x;
 x=5; x=5;
 x=8; x=8;
 +</code>
 +<code>
 -[ERROR]-> Id: x -[ERROR]-> Id: x
            FATAL: Setting immutable parameter that has already been set            FATAL: Setting immutable parameter that has already been set
Line 72: Line 76:
 parameter variables as //immutable types//---they can only be parameter variables as //immutable types//---they can only be
 defined once. defined once.
 +
  
 ===== Array and subrange connections ===== ===== Array and subrange connections =====
Line 82: Line 87:
 nodes ''y[10]'', ..., ''y[19]'' respectively. nodes ''y[10]'', ..., ''y[19]'' respectively.
  
-<code>+<code act>
 bool x[10]; bool x[10];
 bool y[10..19]; bool y[10..19];
Line 90: Line 95:
 Connecting two arrays of differing sizes is an error. Connecting two arrays of differing sizes is an error.
  
-<code>+<code act>
 bool x[10]; bool x[10];
 bool y[10..20]; bool y[10..20];
 x=y; x=y;
 +</code>
 +<code>
 -[ERROR]-> Connection: x = y -[ERROR]-> Connection: x = y
              LHS: bool[10]              LHS: bool[10]
Line 106: Line 113:
 ''y[16]''. ''y[16]''.
  
-<code>+<code act>
 x[3..7] = y[12..16]; x[3..7] = y[12..16];
 </code> </code>
Line 125: Line 132:
 so on. so on.
  
-<code>+<code act>
 bool x[3..4][5..6]; bool x[3..4][5..6];
 bool y[2][2]; bool y[2][2];
Line 134: Line 141:
 become aliases for each other. So while the connection statement become aliases for each other. So while the connection statement
  
-<code>+<code act>
 x[3..4][5..6] = y[0..1][0..1]; x[3..4][5..6] = y[0..1][0..1];
 </code> </code>
Line 143: Line 150:
 visible in the case of sparse arrays. visible in the case of sparse arrays.
  
-<code>+<code act>
 bool x[3..4][5..6]; bool x[3..4][5..6];
 bool y[2][2]; bool y[2][2];
 x = y; x = y;
 bool x[5..5][5..5]; bool x[5..5][5..5];
 +</code>
 +<code>
 -[ERROR]-> Array being extended after it has participated in a connection -[ERROR]-> Array being extended after it has participated in a connection
              Type: bool[ [3..4][5..6]+[5..5][5..5] ]              Type: bool[ [3..4][5..6]+[5..5][5..5] ]
Line 177: Line 186:
 it in braces. it in braces.
  
-<code>+<code act>
 bool x[3]; bool x[3];
 bool x0,x1,x2; bool x0,x1,x2;
Line 197: Line 206:
 (excluding the left-most dimension). (excluding the left-most dimension).
  
-<code>+<code act>
 bool x[5]; bool x[5];
 bool y[3]; bool y[3];
Line 211: Line 220:
 list of lower dimensional arrays enclosed in braces. list of lower dimensional arrays enclosed in braces.
  
-<code>+<code act>
 bool x[2]; bool x[2];
 bool y[2]; bool y[2];
Line 230: Line 239:
 row and one column from a two-dimensional array. row and one column from a two-dimensional array.
  
-<code>+<code act>
 bool row[4],col[4]; bool row[4],col[4];
 bool y[4][4]; bool y[4][4];
Line 241: Line 250:
 following is a valid connection statement: following is a valid connection statement:
  
-<code>+<code act>
 bool a[2][4]; bool a[2][4];
 bool b[4..4][4..7]; bool b[4..4][4..7];
Line 268: Line 277:
 implements an ''int<1>''.  implements an ''int<1>''. 
  
-<code>+<code act>
 int<1> x; int<1> x;
 d1of2 y; d1of2 y;
Line 289: Line 298:
 recommended one. It is only being used to illusrate how connections behave.) recommended one. It is only being used to illusrate how connections behave.)
  
-<code>+<code act>
 chp { chp {
    x:=1;    x:=1;
Line 306: Line 315:
 code. Consider the following scenario: code. Consider the following scenario:
  
-<code>+<code act>
 int<2> ivar; int<2> ivar;
 d1of4 x; d1of4 x;
Line 312: Line 321:
 </code> </code>
  
-Now the operation ''x=ivar''@ is legal, and so is+Now the operation ''x=ivar'' is legal, and so is
 ''y=ivar''. However, if both connections are attempted, it is an ''y=ivar''. However, if both connections are attempted, it is an
 error. This is because one cannot connect a ''d1of4'' type to a error. This is because one cannot connect a ''d1of4'' type to a
Line 328: Line 337:
 situation, where ''bar'' and ''baz'' are both subtypes of ''foo''. situation, where ''bar'' and ''baz'' are both subtypes of ''foo''.
  
-<code>+<code act>
 foo f1; foo f1;
 bar b1; bar b1;
Line 348: Line 357:
 escape type definition boundaries, types used in the port list must be escape type definition boundaries, types used in the port list must be
 the most specific ones possible given the body of the type. the most specific ones possible given the body of the type.
 +
 +==== Port connections ====
 +When instantiating a variable of a user-defined type, the variables in
 +the parameter list can be connected to other variables by using a
 +mechanism akin to parameter passing.
 +
 +<code act>
 +defproc dualrail (bool d0, d1, a)
 +{
 +  spec {
 +    exclhi(d0,d1)  // exclusive high directive
 +  }
 +}
 +  
 +bool d0,d1,da;
 +dualrail c(d0,d1,da);
 +</code>
 +
 +In the example above, nodes ''d0'', ''d1'', and ''da'' are
 +connected to ''c.d0'', ''c.d1'', and ''c.da'' respectively.
 +Nodes can be omitted from the connection list. The following statement
 +connects ''d1'' to ''c.d1'' after instantiating ''c''.
 +
 +<code act>
 +dualrail c(,d1,);
 +</code>
 +
 +Since parameter passing is treated as a connection, all the varied
 +connection mechanisms are supported in parameter lists as well.
 +
 +Two other mechanisms for connecting ports are supported. The first
 +mechanism omits the type name.  The example below is equivalent to the
 +one we just saw.
 +
 +<code act>
 +dualrail c;
 +
 +c(,d1,);
 +</code>
 +
 +While this may appear to not be useful (since the earlier example is
 +shorter), it can be helpful in the context of array declarations. For
 +example, consider the following scenario:
 +
 +<code act>
 +dualrail c[4];
 +bool d1[4];
 +
 +(i:4: c[i](,d1[i],); )
 +</code>
 +
 +A second mechanism is useful to avoid having to remember the order of
 +ports in a process definition. Instead of using the port list of the
 +form where we simply specify the instance to be passed in to the port,
 +we can instead use the following syntax.
 +
 +<code act>
 +bool d1;
 +dualrail c(.d1=d1);
 +
 +dualrail x[4];
 +bool xd1, xd0;
 +
 +x[0](.d1=xd1,.d0=xd0);
 +</code>
  
language/connections.1555611263.txt.gz · Last modified: 2020/12/02 01:00 (external edit)
Except where otherwise noted, content on this wiki is licensed under the following license: GNU Free Documentation License 1.3


  • Show page
  • Old revisions
  • Backlinks
  • Recent Changes
  • Media Manager
  • Sitemap