function $ParseProvider() {
  var cacheDefault = createMap();
  var cacheExpensive = createMap();
  var literals = {
    'true': true,
    'false': false,
    'null': null,
    'undefined': undefined
  };
  var identStart, identContinue;

  /**
   * @ngdoc method
   * @name $parseProvider#addLiteral
   * @description
   *
   * Configure $parse service to add literal values that will be present as literal at expressions.
   *
   * @param {string} literalName Token for the literal value. The literal name value must be a valid literal name.
   * @param {*} literalValue Value for this literal. All literal values must be primitives or `undefined`.
   *
   **/
  this.addLiteral = function(literalName, literalValue) {
    literals[literalName] = literalValue;
  };

 /**
  * @ngdoc method
  * @name $parseProvider#setIdentifierFns
  * @description
  *
  * Allows defining the set of characters that are allowed in Angular expressions. The function
  * `identifierStart` will get called to know if a given character is a valid character to be the
  * first character for an identifier. The function `identifierContinue` will get called to know if
  * a given character is a valid character to be a follow-up identifier character. The functions
  * `identifierStart` and `identifierContinue` will receive as arguments the single character to be
  * identifier and the character code point. These arguments will be `string` and `numeric`. Keep in
  * mind that the `string` parameter can be two characters long depending on the character
  * representation. It is expected for the function to return `true` or `false`, whether that
  * character is allowed or not.
  *
  * Since this function will be called extensivelly, keep the implementation of these functions fast,
  * as the performance of these functions have a direct impact on the expressions parsing speed.
  *
  * @param {function=} identifierStart The function that will decide whether the given character is
  *   a valid identifier start character.
  * @param {function=} identifierContinue The function that will decide whether the given character is
  *   a valid identifier continue character.
  */
  this.setIdentifierFns = function(identifierStart, identifierContinue) {
    identStart = identifierStart;
    identContinue = identifierContinue;
    return this;
  };

  this.$get = ['$filter', function($filter) {
    var noUnsafeEval = csp().noUnsafeEval;
    var $parseOptions = {
          csp: noUnsafeEval,
          expensiveChecks: false,
          literals: copy(literals),
          isIdentifierStart: isFunction(identStart) && identStart,
          isIdentifierContinue: isFunction(identContinue) && identContinue
        },
        $parseOptionsExpensive = {
          csp: noUnsafeEval,
          expensiveChecks: true,
          literals: copy(literals),
          isIdentifierStart: isFunction(identStart) && identStart,
          isIdentifierContinue: isFunction(identContinue) && identContinue
        };
    var runningChecksEnabled = false;

    $parse.$$runningExpensiveChecks = function() {
      return runningChecksEnabled;
    };

    return $parse;

    function $parse(exp, interceptorFn, expensiveChecks) {
      var parsedExpression, oneTime, cacheKey;

      expensiveChecks = expensiveChecks || runningChecksEnabled;

      switch (typeof exp) {
        case 'string':
          exp = exp.trim();
          cacheKey = exp;

          var cache = (expensiveChecks ? cacheExpensive : cacheDefault);
          parsedExpression = cache[cacheKey];

          if (!parsedExpression) {
            if (exp.charAt(0) === ':' && exp.charAt(1) === ':') {
              oneTime = true;
              exp = exp.substring(2);
            }
            var parseOptions = expensiveChecks ? $parseOptionsExpensive : $parseOptions;
            var lexer = new Lexer(parseOptions);
            var parser = new Parser(lexer, $filter, parseOptions);
            parsedExpression = parser.parse(exp);
            if (parsedExpression.constant) {
              parsedExpression.$$watchDelegate = constantWatchDelegate;
            } else if (oneTime) {
              parsedExpression.$$watchDelegate = parsedExpression.literal ?
                  oneTimeLiteralWatchDelegate : oneTimeWatchDelegate;
            } else if (parsedExpression.inputs) {
              parsedExpression.$$watchDelegate = inputsWatchDelegate;
            }
            if (expensiveChecks) {
              parsedExpression = expensiveChecksInterceptor(parsedExpression);
            }
            cache[cacheKey] = parsedExpression;
          }
          return addInterceptor(parsedExpression, interceptorFn);

        case 'function':
          return addInterceptor(exp, interceptorFn);

        default:
          return addInterceptor(noop, interceptorFn);
      }
    }

    function expensiveChecksInterceptor(fn) {
      if (!fn) return fn;
      expensiveCheckFn.$$watchDelegate = fn.$$watchDelegate;
      expensiveCheckFn.assign = expensiveChecksInterceptor(fn.assign);
      expensiveCheckFn.constant = fn.constant;
      expensiveCheckFn.literal = fn.literal;
      for (var i = 0; fn.inputs && i < fn.inputs.length; ++i) {
        fn.inputs[i] = expensiveChecksInterceptor(fn.inputs[i]);
      }
      expensiveCheckFn.inputs = fn.inputs;

      return expensiveCheckFn;

      function expensiveCheckFn(scope, locals, assign, inputs) {
        var expensiveCheckOldValue = runningChecksEnabled;
        runningChecksEnabled = true;
        try {
          return fn(scope, locals, assign, inputs);
        } finally {
          runningChecksEnabled = expensiveCheckOldValue;
        }
      }
    }

    function expressionInputDirtyCheck(newValue, oldValueOfValue) {

      if (newValue == null || oldValueOfValue == null) { // null/undefined
        return newValue === oldValueOfValue;
      }

      if (typeof newValue === 'object') {

        // attempt to convert the value to a primitive type
        // TODO(docs): add a note to docs that by implementing valueOf even objects and arrays can
        //             be cheaply dirty-checked
        newValue = getValueOf(newValue);

        if (typeof newValue === 'object') {
          // objects/arrays are not supported - deep-watching them would be too expensive
          return false;
        }

        // fall-through to the primitive equality check
      }

      //Primitive or NaN
      return newValue === oldValueOfValue || (newValue !== newValue && oldValueOfValue !== oldValueOfValue);
    }

    function inputsWatchDelegate(scope, listener, objectEquality, parsedExpression, prettyPrintExpression) {
      var inputExpressions = parsedExpression.inputs;
      var lastResult;

      if (inputExpressions.length === 1) {
        var oldInputValueOf = expressionInputDirtyCheck; // init to something unique so that equals check fails
        inputExpressions = inputExpressions[0];
        return scope.$watch(function expressionInputWatch(scope) {
          var newInputValue = inputExpressions(scope);
          if (!expressionInputDirtyCheck(newInputValue, oldInputValueOf)) {
            lastResult = parsedExpression(scope, undefined, undefined, [newInputValue]);
            oldInputValueOf = newInputValue && getValueOf(newInputValue);
          }
          return lastResult;
        }, listener, objectEquality, prettyPrintExpression);
      }

      var oldInputValueOfValues = [];
      var oldInputValues = [];
      for (var i = 0, ii = inputExpressions.length; i < ii; i++) {
        oldInputValueOfValues[i] = expressionInputDirtyCheck; // init to something unique so that equals check fails
        oldInputValues[i] = null;
      }

      return scope.$watch(function expressionInputsWatch(scope) {
        var changed = false;

        for (var i = 0, ii = inputExpressions.length; i < ii; i++) {
          var newInputValue = inputExpressions[i](scope);
          if (changed || (changed = !expressionInputDirtyCheck(newInputValue, oldInputValueOfValues[i]))) {
            oldInputValues[i] = newInputValue;
            oldInputValueOfValues[i] = newInputValue && getValueOf(newInputValue);
          }
        }

        if (changed) {
          lastResult = parsedExpression(scope, undefined, undefined, oldInputValues);
        }

        return lastResult;
      }, listener, objectEquality, prettyPrintExpression);
    }

    function oneTimeWatchDelegate(scope, listener, objectEquality, parsedExpression) {
      var unwatch, lastValue;
      return unwatch = scope.$watch(function oneTimeWatch(scope) {
        return parsedExpression(scope);
      }, function oneTimeListener(value, old, scope) {
        lastValue = value;
        if (isFunction(listener)) {
          listener.apply(this, arguments);
        }
        if (isDefined(value)) {
          scope.$$postDigest(function() {
            if (isDefined(lastValue)) {
              unwatch();
            }
          });
        }
      }, objectEquality);
    }

    function oneTimeLiteralWatchDelegate(scope, listener, objectEquality, parsedExpression) {
      var unwatch, lastValue;
      return unwatch = scope.$watch(function oneTimeWatch(scope) {
        return parsedExpression(scope);
      }, function oneTimeListener(value, old, scope) {
        lastValue = value;
        if (isFunction(listener)) {
          listener.call(this, value, old, scope);
        }
        if (isAllDefined(value)) {
          scope.$$postDigest(function() {
            if (isAllDefined(lastValue)) unwatch();
          });
        }
      }, objectEquality);

      function isAllDefined(value) {
        var allDefined = true;
        forEach(value, function(val) {
          if (!isDefined(val)) allDefined = false;
        });
        return allDefined;
      }
    }

    function constantWatchDelegate(scope, listener, objectEquality, parsedExpression) {
      var unwatch;
      return unwatch = scope.$watch(function constantWatch(scope) {
        unwatch();
        return parsedExpression(scope);
      }, listener, objectEquality);
    }

    function addInterceptor(parsedExpression, interceptorFn) {
      if (!interceptorFn) return parsedExpression;
      var watchDelegate = parsedExpression.$$watchDelegate;
      var useInputs = false;

      var regularWatch =
          watchDelegate !== oneTimeLiteralWatchDelegate &&
          watchDelegate !== oneTimeWatchDelegate;

      var fn = regularWatch ? function regularInterceptedExpression(scope, locals, assign, inputs) {
        var value = useInputs && inputs ? inputs[0] : parsedExpression(scope, locals, assign, inputs);
        return interceptorFn(value, scope, locals);
      } : function oneTimeInterceptedExpression(scope, locals, assign, inputs) {
        var value = parsedExpression(scope, locals, assign, inputs);
        var result = interceptorFn(value, scope, locals);
        // we only return the interceptor's result if the
        // initial value is defined (for bind-once)
        return isDefined(value) ? result : value;
      };

      // Propagate $$watchDelegates other then inputsWatchDelegate
      if (parsedExpression.$$watchDelegate &&
          parsedExpression.$$watchDelegate !== inputsWatchDelegate) {
        fn.$$watchDelegate = parsedExpression.$$watchDelegate;
      } else if (!interceptorFn.$stateful) {
        // If there is an interceptor, but no watchDelegate then treat the interceptor like
        // we treat filters - it is assumed to be a pure function unless flagged with $stateful
        fn.$$watchDelegate = inputsWatchDelegate;
        useInputs = !parsedExpression.inputs;
        fn.inputs = parsedExpression.inputs ? parsedExpression.inputs : [parsedExpression];
      }

      return fn;
    }
  }];
}
@ngdoc provider
@name $parseProvider

@description
`$parseProvider` can be used for configuring the default behavior of the {@link ng.$parse $parse}
 service.