Keysymbols: &, ~&, |, ~|, ^, ~^, ^~.
The reduction operators are and, nand, or, nor, xor xnor and an alternative xnor. They take one operand and perform a bit-by-next-bit operation, starting with the two leftmost bits, giving a 1-bit result.
module reductTest;
reg [3:0] a, b ,c;
initial begin
a = 4'b1111;
b = 4'b0101;
c = 4'b0011;
$displayb(& a); // bitwise and, (same as 1&1&1&1), evaluates to 1
$displayb(| b); // bitwise or, (same as 0|1|0|1), evaluates to 1
$displayb(^ b); // bitwise xor, (same as 0^1^0^1), evaluates to 0
end
endmodule // reductTest
Please note carefully the differences in logical, bitwise and reduction operators. The symbols for bitwise and reduction overlap but the number of operands is different in those cases.
EXERCISE
What do the following evaluate to ?
$displayb(& 1'b10);
$displayb(| 3'b101x);
$displayb(^ 4'b1101);