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e Operators
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e language includes all the operators of the regular programming language, and few additional ones.
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Bit Wise Operators
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Bit wise operators work at bit level, so they are called bit wise operators. Below table list each operator and its description.
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Operator
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Description
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~
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Unary bitwise negation
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&
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Binary bitwise AND
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Binary bitwise OR
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^
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Binary bitwise XOR
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>>
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Shift bits right
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<<
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Shift bits left
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Example - Bit Wise Operator
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1 <'
2 extend sys {
3 run() is also {
4 var a : byte;
5 var b : byte;
6 var c : byte;
7 a = 0xAA;
8 b = 0x55;
9 outf (" a = %b b = %b\n", a, b);
10 // Bitwise negation
11 c = ~a;
12 outf ("Bitwise negation a is :%b\n", c);
13 // Bitwise AND operation
14 c = a & b;
15 outf ("Bitwise AND of a with b is :%b\n", c);
16 // Bitwise OR operation
17 c = a | b;
18 outf ("Bitwise OR of a with b is :%b\n", c);
19 // Bitwise XOR operation
20 c = a ^ b;
21 outf ("Bitwise XOR of a with b is :%b\n", c);
22 // Left shift
23 c = a << 2;
24 outf ("Left shift a by 2 bits is :%b\n", c);
25 // Right shift
26 c = b >> 2;
27 outf ("Right shift b by 2 bits is :%b\n", c);
28 };
29 };
30 '>
You could download file e_basics5.e
here
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Specman Output
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a = 10101010 b = 1010101
Bitwise negation a is :1010101
Bitwise AND of a with b is :0
Bitwise OR of a with b is :11111111
Bitwise XOR of a with b is :11111111
Left shift a by 2 bits is :10101000
Right shift b by 2 bits is :10101
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Boolean Operators
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Boolean operators are used in condition checking as in other languages. Below table shows e boolean operators
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Operator
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Description
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! (not)
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Returns TRUE when an expression evaluates to FALSE, and vice versa.
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&& (and)
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Returns TRUE if two expressions are both TRUE.
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|| (or)
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Returns TRUE if one of two expressions is TRUE.
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=>
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Returns TRUE when the first expression of two expressions is FALSE, or when both expressions are TRUE.
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now
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Returns TRUE if an event has occurred in the current cycle.
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Example - Boolean Operators
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1 <'
2 extend sys {
3 run() is also {
4 var a : bool;
5 var b : bool;
6 var c : bool;
7 var d : bool;
8 outf (" a = %b b = %b c = %b\n", a, b,c);
9 // Not Operator
10 d = ! (TRUE);
11 outf ("Not of (TRUE) is :%b\n", d);
12 // Boolean AND operation
13 d = a && c;
14 outf ("Boolean AND of a with c is :%b\n", d);
15 // Boolean OR operation
16 d = a || b;
17 outf ("Boolean OR of a with b is :%b\n", d);
18 // Boolean implication operation
19 d = (2 > 3) => (3 > 2);
20 outf ("Boolean implication of (2 > 3) => (3 > 2) :%b\n", d);
21 // Boolean implication operation
22 d = (4 > 3) => (3 > 4);
23 outf ("Boolean implication of (4 > 3) => (3 > 4) :%b\n", d);
24 // Below code does not make sense
25 if now @sys.any then {
26 out("sys.any occurred");
27 };
28 };
29 };
30 '>
You could download file e_basics6.e
here
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Specman Output
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a = 0 b = 0 c = 0
Not of (TRUE) is :0
Boolean AND of a with c is :0
Boolean OR of a with b is :0
Boolean implication of (2 > 3) => (3 > 2) :1
Boolean implication of (4 > 3) => (3 > 4) :0
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Arithmetic Operators
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Arithmetic operators are same in any other programming language.
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Operator
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Description
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Unary +
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Unary plus
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Unary -
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Unary minus
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+
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Binary addition
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-
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Binary addition
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Example - Arithmetic Operators
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1 <'
2 extend sys {
3 run() is also {
4 out("10 = ",+10);
5 out("-10 = ",-10);
6 out("10+10 = ", 10 +10);
7 out("10-1 = ", 10 -1);
8 out("10*2 = ", 10 *2);
9 out("10/2 = ", 10 /2);
10 out("10%3 = ", 10 %3);
11 };
12 };
13 '>
You could download file e_basics7.e
here
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Specman Output
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10 = 10
-10 = -10
10+10 = 20
10-1 = 9
10*2 = 20
10/2 = 5
10%3 = 1
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Comparison Operators
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Same as in Verilog, and few more
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Operator
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Description
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<<=>>=
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Compares two numeric expressions or HDL pathnames.
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== !=
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Determines whether two expressions are equal or not.
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=== !==
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Performs a 4-state, Verilog-style comparison of HDL objects.
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~ !~
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Determines whether two string expressions are equal or not.
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in
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Determines whether an expression is in a list or a range.
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String Matching
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String matching is performed with AWK-style regular expressions. You can use the standard AWK regular expression notation to write complex patterns. This notation uses the /&/ format for the pattern to specify AWK-style regular expression syntax.
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Extraction and Concatenation Operators
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Operator
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Description
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[ ]
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Extracts or sets a single item from a list.
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[ ; ]
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Extracts or sets consecutive bits or slices of a scalar, a list of bits, or a list of bytes.
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[ .. ]
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List slicing operator
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[ range,...]
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Range list operator
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{ ; }
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List concatenation
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%{&}
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Bit concatenation
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