// (C) 2001-2020, Daniel Kroening, Edmund Clarke,
// Computer Science Department, University of Oxford
// Computer Science Department, Carnegie Mellon University
//
// All rights reserved. Redistribution and use in source and binary forms, with
// or without modification, are permitted provided that the following
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//
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//      notice, this list of conditions and the following disclaimer.
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//   2. Redistributions in binary form must reproduce the above copyright
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//
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// You can contact the author at:
//   - homepage : https://www.cprover.org/ebmc/
//   - source repository : https://github.com/diffblue/hw-cbmc

module main(input clk);

  reg [31:0] x = 0;

  always @(posedge clk)
    x<=x+1;

  // Starting from a particular state,
  // first_match yields the sequence that _ends_ first.

  // fails
  initial p0: assert property ((##1 1) or (##2 1) |-> x==1);

  // passes
  initial p1: assert property (first_match((##1 1) or (##2 1)) |-> x==1);

  // fails
  initial p2: assert property (1 or ##1 1 |-> x==0);

  // passes
  initial p3: assert property (first_match(1 or ##1 1) |-> x==0);

endmodule