tools/src/cnf/ops.go

// Copyright 2023 The Dawn & Tint Authors
//
// 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.
//
// 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.
//
// 3. Neither the name of the copyright holder nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

package cnf

import "dawn.googlesource.com/dawn/tools/src/transform"

// And returns a new expression that represents (lhs ∧ rhs)
func And(lhs, rhs Expr) Expr {
	return append(append(Expr{}, lhs...), rhs...)
}

// Or returns a new expression that represents (lhs ∨ rhs)
func Or(lhs, rhs Expr) Expr {
	if len(lhs) == 0 {
		return rhs
	}
	if len(rhs) == 0 {
		return lhs
	}
	out := Expr{}
	for _, aOrs := range lhs {
		for _, bOrs := range rhs {
			out = append(out, append(append(Ors{}, aOrs...), bOrs...))
		}
	}
	return out
}

// Not returns a new expression that represents (¬expr)
func Not(expr Expr) Expr {
	// Transform each of the OR expressions into AND expressions where each unary is negated.
	out := Expr{}
	for _, o := range expr {
		ands, _ := transform.Slice(o, func(u Unary) (Ors, error) {
			return Ors{Unary{Negate: !u.Negate, Var: u.Var}}, nil
		})
		out = Or(out, ands)
	}
	return out
}