src/cengines/replacer/decompositionrule.js

/*
 * Copyright (c) 2018 Isaac Phoenix (tearsofphoenix@icloud.com).
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import {BasicGate} from '../../ops/basics'
import { isKindclassOf } from '../../libs/util'

/**
 * @class DecompositionRule
 * @desc A rule for breaking down specific gates into sequences of simpler gates.
 */
export default class DecompositionRule {
  /**
   * @constructor
    @param {function} gateClass The type of gate that this rule decomposes.

    The gate class is redundant information used to make lookups
faster when iterating over a circuit and deciding "which rules
apply to this gate?" again and again.

    Note that this parameter is a gate type, not a gate instance.
    You supply gate_class=MyGate or gate_class=MyGate().__class__,
    not gate_class=MyGate().

   @param {function} gateDecomposer Function which,
    given the command to decompose, applies a sequence of gates
corresponding to the high-level function of a gate of type
gate_class.

   @param {function} gateRecognizer A
predicate that determines if the decomposition applies to the
given command (on top of the filtering by gate_class).

For example, a decomposition rule may only to apply rotation
gates that rotate by a specific angle.

    If no gate_recognizer is given, the decomposition applies to
all gates matching the gate_class.
     */
  constructor(gateClass, gateDecomposer, gateRecognizer = () => true) {
    // Check for common gate_class type mistakes.
    if (gateClass instanceof BasicGate) {
      throw new Error('gate_class is a gate instance instead of a type of BasicGate.'
            + '\nDid you pass in someGate instead of someGate.__class__?')
    }

    if (!isKindclassOf(gateClass, BasicGate)) {
      throw new Error('Invalid class type, you should pass a subclass of BasicGate!')
    }

    this.gateClass = gateClass
    this.gateDecomposer = gateDecomposer
    this.gateRecognizer = gateRecognizer
  }
}