// SPDX-FileCopyrightText: 2001-2020 Daniel Kroening, Edmund Clarke
// SPDX-License-Identifier: BSD-3-Clause
//
// (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
// conditions are met:
//
//   1. Redistributions of source code must retain the above copyright
//      notice, this list of conditions and the following disclaimer.
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//   2. Redistributions in binary form must reproduce the above copyright
//      notice, this list of conditions and the following disclaimer in the
//      documentation and/or other materials provided with the distribution.
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//      without specific prior written permission.
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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
