@cesium/engine/Source/Scene/Expression.js

CesiumJS is a JavaScript library for creating 3D globes and 2D maps in a web browser without a plugin.

import Cartesian2 from "../Core/Cartesian2.js";
import Cartesian3 from "../Core/Cartesian3.js";
import Cartesian4 from "../Core/Cartesian4.js";
import Check from "../Core/Check.js";
import Color from "../Core/Color.js";
import defined from "../Core/defined.js";
import DeveloperError from "../Core/DeveloperError.js";
import CesiumMath from "../Core/Math.js";
import RuntimeError from "../Core/RuntimeError.js";
import jsep from "jsep";
import ExpressionNodeType from "./ExpressionNodeType.js";

/**
 * An expression for a style applied to a {@link Cesium3DTileset}.
 * <p>
 * Evaluates an expression defined using the
 * {@link https://github.com/CesiumGS/3d-tiles/tree/main/specification/Styling|3D Tiles Styling language}.
 * </p>
 * <p>
 * Implements the {@link StyleExpression} interface.
 * </p>
 *
 * @alias Expression
 * @constructor
 *
 * @param {string} [expression] The expression defined using the 3D Tiles Styling language.
 * @param {object} [defines] Defines in the style.
 *
 * @example
 * const expression = new Cesium.Expression('(regExp("^Chest").test(${County})) && (${YearBuilt} >= 1970)');
 * expression.evaluate(feature); // returns true or false depending on the feature's properties
 *
 * @example
 * const expression = new Cesium.Expression('(${Temperature} > 90) ? color("red") : color("white")');
 * expression.evaluateColor(feature, result); // returns a Cesium.Color object
 */
function Expression(expression, defines) {
  //>>includeStart('debug', pragmas.debug);
  Check.typeOf.string("expression", expression);
  //>>includeEnd('debug');

  this._expression = expression;
  expression = replaceDefines(expression, defines);
  expression = replaceVariables(removeBackslashes(expression));

  // customize jsep operators
  jsep.addBinaryOp("=~", 0);
  jsep.addBinaryOp("!~", 0);

  let ast;
  try {
    ast = jsep(expression);
  } catch (e) {
    throw new RuntimeError(e);
  }

  this._runtimeAst = createRuntimeAst(this, ast);
}

Object.defineProperties(Expression.prototype, {
  /**
   * Gets the expression defined in the 3D Tiles Styling language.
   *
   * @memberof Expression.prototype
   *
   * @type {string}
   * @readonly
   *
   * @default undefined
   */
  expression: {
    get: function () {
      return this._expression;
    },
  },
});

// Scratch storage manager while evaluating deep expressions.
// For example, an expression like dot(vec4(${red}), vec4(${green}) * vec4(${blue}) requires 3 scratch Cartesian4's
const scratchStorage = {
  arrayIndex: 0,
  arrayArray: [[]],
  cartesian2Index: 0,
  cartesian3Index: 0,
  cartesian4Index: 0,
  cartesian2Array: [new Cartesian2()],
  cartesian3Array: [new Cartesian3()],
  cartesian4Array: [new Cartesian4()],
  reset: function () {
    this.arrayIndex = 0;
    this.cartesian2Index = 0;
    this.cartesian3Index = 0;
    this.cartesian4Index = 0;
  },
  getArray: function () {
    if (this.arrayIndex >= this.arrayArray.length) {
      this.arrayArray.push([]);
    }
    const array = this.arrayArray[this.arrayIndex++];
    array.length = 0;
    return array;
  },
  getCartesian2: function () {
    if (this.cartesian2Index >= this.cartesian2Array.length) {
      this.cartesian2Array.push(new Cartesian2());
    }
    return this.cartesian2Array[this.cartesian2Index++];
  },
  getCartesian3: function () {
    if (this.cartesian3Index >= this.cartesian3Array.length) {
      this.cartesian3Array.push(new Cartesian3());
    }
    return this.cartesian3Array[this.cartesian3Index++];
  },
  getCartesian4: function () {
    if (this.cartesian4Index >= this.cartesian4Array.length) {
      this.cartesian4Array.push(new Cartesian4());
    }
    return this.cartesian4Array[this.cartesian4Index++];
  },
};

/**
 * Evaluates the result of an expression, optionally using the provided feature's properties. If the result of
 * the expression in the
 * {@link https://github.com/CesiumGS/3d-tiles/tree/main/specification/Styling|3D Tiles Styling language}
 * is of type <code>Boolean</code>, <code>Number</code>, or <code>String</code>, the corresponding JavaScript
 * primitive type will be returned. If the result is a <code>RegExp</code>, a Javascript <code>RegExp</code>
 * object will be returned. If the result is a <code>Cartesian2</code>, <code>Cartesian3</code>, or <code>Cartesian4</code>,
 * a {@link Cartesian2}, {@link Cartesian3}, or {@link Cartesian4} object will be returned. If the <code>result</code> argument is
 * a {@link Color}, the {@link Cartesian4} value is converted to a {@link Color} and then returned.
 *
 * @param {Cesium3DTileFeature} feature The feature whose properties may be used as variables in the expression.
 * @param {object} [result] The object onto which to store the result.
 * @returns {boolean|number|string|RegExp|Cartesian2|Cartesian3|Cartesian4|Color} The result of evaluating the expression.
 */
Expression.prototype.evaluate = function (feature, result) {
  scratchStorage.reset();
  const value = this._runtimeAst.evaluate(feature);
  if (result instanceof Color && value instanceof Cartesian4) {
    return Color.fromCartesian4(value, result);
  }
  if (
    value instanceof Cartesian2 ||
    value instanceof Cartesian3 ||
    value instanceof Cartesian4
  ) {
    return value.clone(result);
  }
  return value;
};

/**
 * Evaluates the result of a Color expression, optionally using the provided feature's properties.
 * <p>
 * This is equivalent to {@link Expression#evaluate} but always returns a {@link Color} object.
 * </p>
 *
 * @param {Cesium3DTileFeature} feature The feature whose properties may be used as variables in the expression.
 * @param {Color} [result] The object in which to store the result
 * @returns {Color} The modified result parameter or a new Color instance if one was not provided.
 */
Expression.prototype.evaluateColor = function (feature, result) {
  scratchStorage.reset();
  const color = this._runtimeAst.evaluate(feature);
  return Color.fromCartesian4(color, result);
};

/**
 * Gets the shader function for this expression.
 * Returns undefined if the shader function can't be generated from this expression.
 *
 * @param {string} functionSignature Signature of the generated function.
 * @param {object} variableSubstitutionMap Maps variable names to shader variable names.
 * @param {object} shaderState Stores information about the generated shader function, including whether it is translucent.
 * @param {string} returnType The return type of the generated function.
 *
 * @returns {string} The shader function.
 *
 * @private
 */
Expression.prototype.getShaderFunction = function (
  functionSignature,
  variableSubstitutionMap,
  shaderState,
  returnType,
) {
  let shaderExpression = this.getShaderExpression(
    variableSubstitutionMap,
    shaderState,
  );

  shaderExpression =
    `${returnType} ${functionSignature}\n` +
    `{\n` +
    `    return ${shaderExpression};\n` +
    `}\n`;

  return shaderExpression;
};

/**
 * Gets the shader expression for this expression.
 * Returns undefined if the shader expression can't be generated from this expression.
 *
 * @param {object} variableSubstitutionMap Maps variable names to shader variable names.
 * @param {object} shaderState Stores information about the generated shader function, including whether it is translucent.
 *
 * @returns {string} The shader expression.
 *
 * @private
 */
Expression.prototype.getShaderExpression = function (
  variableSubstitutionMap,
  shaderState,
) {
  return this._runtimeAst.getShaderExpression(
    variableSubstitutionMap,
    shaderState,
  );
};

/**
 * Gets the variables used by the expression.
 *
 * @returns {string[]} The variables used by the expression.
 *
 * @private
 */
Expression.prototype.getVariables = function () {
  let variables = [];

  this._runtimeAst.getVariables(variables);

  // Remove duplicates
  variables = variables.filter(function (variable, index, variables) {
    return variables.indexOf(variable) === index;
  });

  return variables;
};

const unaryOperators = ["!", "-", "+"];
const binaryOperators = [
  "+",
  "-",
  "*",
  "/",
  "%",
  "===",
  "!==",
  ">",
  ">=",
  "<",
  "<=",
  "&&",
  "||",
  "!~",
  "=~",
];

const variableRegex = /\${(.*?)}/g; // Matches ${variable_name}
const backslashRegex = /\\/g;
const backslashReplacement = "@#%";
const replacementRegex = /@#%/g;

const scratchColor = new Color();

const unaryFunctions = {
  abs: getEvaluateUnaryComponentwise(Math.abs),
  sqrt: getEvaluateUnaryComponentwise(Math.sqrt),
  cos: getEvaluateUnaryComponentwise(Math.cos),
  sin: getEvaluateUnaryComponentwise(Math.sin),
  tan: getEvaluateUnaryComponentwise(Math.tan),
  acos: getEvaluateUnaryComponentwise(Math.acos),
  asin: getEvaluateUnaryComponentwise(Math.asin),
  atan: getEvaluateUnaryComponentwise(Math.atan),
  radians: getEvaluateUnaryComponentwise(CesiumMath.toRadians),
  degrees: getEvaluateUnaryComponentwise(CesiumMath.toDegrees),
  sign: getEvaluateUnaryComponentwise(CesiumMath.sign),
  floor: getEvaluateUnaryComponentwise(Math.floor),
  ceil: getEvaluateUnaryComponentwise(Math.ceil),
  round: getEvaluateUnaryComponentwise(Math.round),
  exp: getEvaluateUnaryComponentwise(Math.exp),
  exp2: getEvaluateUnaryComponentwise(exp2),
  log: getEvaluateUnaryComponentwise(Math.log),
  log2: getEvaluateUnaryComponentwise(log2),
  fract: getEvaluateUnaryComponentwise(fract),
  length: length,
  normalize: normalize,
};

const binaryFunctions = {
  atan2: getEvaluateBinaryComponentwise(Math.atan2, false),
  pow: getEvaluateBinaryComponentwise(Math.pow, false),
  min: getEvaluateBinaryComponentwise(Math.min, true),
  max: getEvaluateBinaryComponentwise(Math.max, true),
  distance: distance,
  dot: dot,
  cross: cross,
};

const ternaryFunctions = {
  clamp: getEvaluateTernaryComponentwise(CesiumMath.clamp, true),
  mix: getEvaluateTernaryComponentwise(CesiumMath.lerp, true),
};

function fract(number) {
  return number - Math.floor(number);
}

function exp2(exponent) {
  return Math.pow(2.0, exponent);
}

function log2(number) {
  return CesiumMath.log2(number);
}

function getEvaluateUnaryComponentwise(operation) {
  return function (call, left) {
    if (typeof left === "number") {
      return operation(left);
    } else if (left instanceof Cartesian2) {
      return Cartesian2.fromElements(
        operation(left.x),
        operation(left.y),
        scratchStorage.getCartesian2(),
      );
    } else if (left instanceof Cartesian3) {
      return Cartesian3.fromElements(
        operation(left.x),
        operation(left.y),
        operation(left.z),
        scratchStorage.getCartesian3(),
      );
    } else if (left instanceof Cartesian4) {
      return Cartesian4.fromElements(
        operation(left.x),
        operation(left.y),
        operation(left.z),
        operation(left.w),
        scratchStorage.getCartesian4(),
      );
    }
    throw new RuntimeError(
      `Function "${call}" requires a vector or number argument. Argument is ${left}.`,
    );
  };
}

function getEvaluateBinaryComponentwise(operation, allowScalar) {
  return function (call, left, right) {
    if (allowScalar && typeof right === "number") {
      if (typeof left === "number") {
        return operation(left, right);
      } else if (left instanceof Cartesian2) {
        return Cartesian2.fromElements(
          operation(left.x, right),
          operation(left.y, right),
          scratchStorage.getCartesian2(),
        );
      } else if (left instanceof Cartesian3) {
        return Cartesian3.fromElements(
          operation(left.x, right),
          operation(left.y, right),
          operation(left.z, right),
          scratchStorage.getCartesian3(),
        );
      } else if (left instanceof Cartesian4) {
        return Cartesian4.fromElements(
          operation(left.x, right),
          operation(left.y, right),
          operation(left.z, right),
          operation(left.w, right),
          scratchStorage.getCartesian4(),
        );
      }
    }

    if (typeof left === "number" && typeof right === "number") {
      return operation(left, right);
    } else if (left instanceof Cartesian2 && right instanceof Cartesian2) {
      return Cartesian2.fromElements(
        operation(left.x, right.x),
        operation(left.y, right.y),
        scratchStorage.getCartesian2(),
      );
    } else if (left instanceof Cartesian3 && right instanceof Cartesian3) {
      return Cartesian3.fromElements(
        operation(left.x, right.x),
        operation(left.y, right.y),
        operation(left.z, right.z),
        scratchStorage.getCartesian3(),
      );
    } else if (left instanceof Cartesian4 && right instanceof Cartesian4) {
      return Cartesian4.fromElements(
        operation(left.x, right.x),
        operation(left.y, right.y),
        operation(left.z, right.z),
        operation(left.w, right.w),
        scratchStorage.getCartesian4(),
      );
    }

    throw new RuntimeError(
      `Function "${call}" requires vector or number arguments of matching types. Arguments are ${left} and ${right}.`,
    );
  };
}

function getEvaluateTernaryComponentwise(operation, allowScalar) {
  return function (call, left, right, test) {
    if (allowScalar && typeof test === "number") {
      if (typeof left === "number" && typeof right === "number") {
        return operation(left, right, test);
      } else if (left instanceof Cartesian2 && right instanceof Cartesian2) {
        return Cartesian2.fromElements(
          operation(left.x, right.x, test),
          operation(left.y, right.y, test),
          scratchStorage.getCartesian2(),
        );
      } else if (left instanceof Cartesian3 && right instanceof Cartesian3) {
        return Cartesian3.fromElements(
          operation(left.x, right.x, test),
          operation(left.y, right.y, test),
          operation(left.z, right.z, test),
          scratchStorage.getCartesian3(),
        );
      } else if (left instanceof Cartesian4 && right instanceof Cartesian4) {
        return Cartesian4.fromElements(
          operation(left.x, right.x, test),
          operation(left.y, right.y, test),
          operation(left.z, right.z, test),
          operation(left.w, right.w, test),
          scratchStorage.getCartesian4(),
        );
      }
    }

    if (
      typeof left === "number" &&
      typeof right === "number" &&
      typeof test === "number"
    ) {
      return operation(left, right, test);
    } else if (
      left instanceof Cartesian2 &&
      right instanceof Cartesian2 &&
      test instanceof Cartesian2
    ) {
      return Cartesian2.fromElements(
        operation(left.x, right.x, test.x),
        operation(left.y, right.y, test.y),
        scratchStorage.getCartesian2(),
      );
    } else if (
      left instanceof Cartesian3 &&
      right instanceof Cartesian3 &&
      test instanceof Cartesian3
    ) {
      return Cartesian3.fromElements(
        operation(left.x, right.x, test.x),
        operation(left.y, right.y, test.y),
        operation(left.z, right.z, test.z),
        scratchStorage.getCartesian3(),
      );
    } else if (
      left instanceof Cartesian4 &&
      right instanceof Cartesian4 &&
      test instanceof Cartesian4
    ) {
      return Cartesian4.fromElements(
        operation(left.x, right.x, test.x),
        operation(left.y, right.y, test.y),
        operation(left.z, right.z, test.z),
        operation(left.w, right.w, test.w),
        scratchStorage.getCartesian4(),
      );
    }

    throw new RuntimeError(
      `Function "${call}" requires vector or number arguments of matching types. Arguments are ${left}, ${right}, and ${test}.`,
    );
  };
}

function length(call, left) {
  if (typeof left === "number") {
    return Math.abs(left);
  } else if (left instanceof Cartesian2) {
    return Cartesian2.magnitude(left);
  } else if (left instanceof Cartesian3) {
    return Cartesian3.magnitude(left);
  } else if (left instanceof Cartesian4) {
    return Cartesian4.magnitude(left);
  }

  throw new RuntimeError(
    `Function "${call}" requires a vector or number argument. Argument is ${left}.`,
  );
}

function normalize(call, left) {
  if (typeof left === "number") {
    return 1.0;
  } else if (left instanceof Cartesian2) {
    return Cartesian2.normalize(left, scratchStorage.getCartesian2());
  } else if (left instanceof Cartesian3) {
    return Cartesian3.normalize(left, scratchStorage.getCartesian3());
  } else if (left instanceof Cartesian4) {
    return Cartesian4.normalize(left, scratchStorage.getCartesian4());
  }

  throw new RuntimeError(
    `Function "${call}" requires a vector or number argument. Argument is ${left}.`,
  );
}

function distance(call, left, right) {
  if (typeof left === "number" && typeof right === "number") {
    return Math.abs(left - right);
  } else if (left instanceof Cartesian2 && right instanceof Cartesian2) {
    return Cartesian2.distance(left, right);
  } else if (left instanceof Cartesian3 && right instanceof Cartesian3) {
    return Cartesian3.distance(left, right);
  } else if (left instanceof Cartesian4 && right instanceof Cartesian4) {
    return Cartesian4.distance(left, right);
  }

  throw new RuntimeError(
    `Function "${call}" requires vector or number arguments of matching types. Arguments are ${left} and ${right}.`,
  );
}

function dot(call, left, right) {
  if (typeof left === "number" && typeof right === "number") {
    return left * right;
  } else if (left instanceof Cartesian2 && right instanceof Cartesian2) {
    return Cartesian2.dot(left, right);
  } else if (left instanceof Cartesian3 && right instanceof Cartesian3) {
    return Cartesian3.dot(left, right);
  } else if (left instanceof Cartesian4 && right instanceof Cartesian4) {
    return Cartesian4.dot(left, right);
  }

  throw new RuntimeError(
    `Function "${call}" requires vector or number arguments of matching types. Arguments are ${left} and ${right}.`,
  );
}

function cross(call, left, right) {
  if (left instanceof Cartesian3 && right instanceof Cartesian3) {
    return Cartesian3.cross(left, right, scratchStorage.getCartesian3());
  }

  throw new RuntimeError(
    `Function "${call}" requires vec3 arguments. Arguments are ${left} and ${right}.`,
  );
}

function Node(type, value, left, right, test) {
  this._type = type;
  this._value = value;
  this._left = left;
  this._right = right;
  this._test = test;
  this.evaluate = undefined;

  setEvaluateFunction(this);
}

function replaceDefines(expression, defines) {
  if (!defined(defines)) {
    return expression;
  }
  for (const key in defines) {
    if (defines.hasOwnProperty(key)) {
      const definePlaceholder = new RegExp(`\\$\\{${key}\\}`, "g");
      const defineReplace = `(${defines[key]})`;
      if (defined(defineReplace)) {
        expression = expression.replace(definePlaceholder, defineReplace);
      }
    }
  }
  return expression;
}

function removeBackslashes(expression) {
  return expression.replace(backslashRegex, backslashReplacement);
}

function replaceBackslashes(expression) {
  return expression.replace(replacementRegex, "\\");
}

function replaceVariables(expression) {
  let exp = expression;
  let result = "";
  let i = exp.indexOf("${");
  while (i >= 0) {
    // Check if string is inside quotes
    const openSingleQuote = exp.indexOf("'");
    const openDoubleQuote = exp.indexOf('"');
    let closeQuote;
    if (openSingleQuote >= 0 && openSingleQuote < i) {
      closeQuote = exp.indexOf("'", openSingleQuote + 1);
      result += exp.substr(0, closeQuote + 1);
      exp = exp.substr(closeQuote + 1);
      i = exp.indexOf("${");
    } else if (openDoubleQuote >= 0 && openDoubleQuote < i) {
      closeQuote = exp.indexOf('"', openDoubleQuote + 1);
      result += exp.substr(0, closeQuote + 1);
      exp = exp.substr(closeQuote + 1);
      i = exp.indexOf("${");
    } else {
      result += exp.substr(0, i);
      const j = exp.indexOf("}");
      if (j < 0) {
        throw new RuntimeError("Unmatched {.");
      }
      result += `czm_${exp.substr(i + 2, j - (i + 2))}`;
      exp = exp.substr(j + 1);
      i = exp.indexOf("${");
    }
  }
  result += exp;
  return result;
}

function parseLiteral(ast) {
  const type = typeof ast.value;
  if (ast.value === null) {
    return new Node(ExpressionNodeType.LITERAL_NULL, null);
  } else if (type === "boolean") {
    return new Node(ExpressionNodeType.LITERAL_BOOLEAN, ast.value);
  } else if (type === "number") {
    return new Node(ExpressionNodeType.LITERAL_NUMBER, ast.value);
  } else if (type === "string") {
    if (ast.value.indexOf("${") >= 0) {
      return new Node(ExpressionNodeType.VARIABLE_IN_STRING, ast.value);
    }
    return new Node(
      ExpressionNodeType.LITERAL_STRING,
      replaceBackslashes(ast.value),
    );
  }
}

function parseCall(expression, ast) {
  const args = ast.arguments;
  const argsLength = args.length;
  let call;
  let val, left, right;

  // Member function calls
  if (ast.callee.type === "MemberExpression") {
    call = ast.callee.property.name;
    const object = ast.callee.object;
    if (call === "test" || call === "exec") {
      // Make sure this is called on a valid type
      if (!defined(object.callee) || object.callee.name !== "regExp") {
        throw new RuntimeError(`${call} is not a function.`);
      }
      if (argsLength === 0) {
        if (call === "test") {
          return new Node(ExpressionNodeType.LITERAL_BOOLEAN, false);
        }
        return new Node(ExpressionNodeType.LITERAL_NULL, null);
      }
      left = createRuntimeAst(expression, object);
      right = createRuntimeAst(expression, args[0]);
      return new Node(ExpressionNodeType.FUNCTION_CALL, call, left, right);
    } else if (call === "toString") {
      val = createRuntimeAst(expression, object);
      return new Node(ExpressionNodeType.FUNCTION_CALL, call, val);
    }

    throw new RuntimeError(`Unexpected function call "${call}".`);
  }

  // Non-member function calls
  call = ast.callee.name;
  if (call === "color") {
    if (argsLength === 0) {
      return new Node(ExpressionNodeType.LITERAL_COLOR, call);
    }
    val = createRuntimeAst(expression, args[0]);
    if (defined(args[1])) {
      const alpha = createRuntimeAst(expression, args[1]);
      return new Node(ExpressionNodeType.LITERAL_COLOR, call, [val, alpha]);
    }
    return new Node(ExpressionNodeType.LITERAL_COLOR, call, [val]);
  } else if (call === "rgb" || call === "hsl") {
    if (argsLength < 3) {
      throw new RuntimeError(`${call} requires three arguments.`);
    }
    val = [
      createRuntimeAst(expression, args[0]),
      createRuntimeAst(expression, args[1]),
      createRuntimeAst(expression, args[2]),
    ];
    return new Node(ExpressionNodeType.LITERAL_COLOR, call, val);
  } else if (call === "rgba" || call === "hsla") {
    if (argsLength < 4) {
      throw new RuntimeError(`${call} requires four arguments.`);
    }
    val = [
      createRuntimeAst(expression, args[0]),
      createRuntimeAst(expression, args[1]),
      createRuntimeAst(expression, args[2]),
      createRuntimeAst(expression, args[3]),
    ];
    return new Node(ExpressionNodeType.LITERAL_COLOR, call, val);
  } else if (call === "vec2" || call === "vec3" || call === "vec4") {
    // Check for invalid constructors at evaluation time
    val = new Array(argsLength);
    for (let i = 0; i < argsLength; ++i) {
      val[i] = createRuntimeAst(expression, args[i]);
    }
    return new Node(ExpressionNodeType.LITERAL_VECTOR, call, val);
  } else if (call === "isNaN" || call === "isFinite") {
    if (argsLength === 0) {
      if (call === "isNaN") {
        return new Node(ExpressionNodeType.LITERAL_BOOLEAN, true);
      }
      return new Node(ExpressionNodeType.LITERAL_BOOLEAN, false);
    }
    val = createRuntimeAst(expression, args[0]);
    return new Node(ExpressionNodeType.UNARY, call, val);
  } else if (call === "isExactClass" || call === "isClass") {
    if (argsLength < 1 || argsLength > 1) {
      throw new RuntimeError(`${call} requires exactly one argument.`);
    }
    val = createRuntimeAst(expression, args[0]);
    return new Node(ExpressionNodeType.UNARY, call, val);
  } else if (call === "getExactClassName") {
    if (argsLength > 0) {
      throw new RuntimeError(`${call} does not take any argument.`);
    }
    return new Node(ExpressionNodeType.UNARY, call);
  } else if (defined(unaryFunctions[call])) {
    if (argsLength !== 1) {
      throw new RuntimeError(`${call} requires exactly one argument.`);
    }
    val = createRuntimeAst(expression, args[0]);
    return new Node(ExpressionNodeType.UNARY, call, val);
  } else if (defined(binaryFunctions[call])) {
    if (argsLength !== 2) {
      throw new RuntimeError(`${call} requires exactly two arguments.`);
    }
    left = createRuntimeAst(expression, args[0]);
    right = createRuntimeAst(expression, args[1]);
    return new Node(ExpressionNodeType.BINARY, call, left, right);
  } else if (defined(ternaryFunctions[call])) {
    if (argsLength !== 3) {
      throw new RuntimeError(`${call} requires exactly three arguments.`);
    }
    left = createRuntimeAst(expression, args[0]);
    right = createRuntimeAst(expression, args[1]);
    const test = createRuntimeAst(expression, args[2]);
    return new Node(ExpressionNodeType.TERNARY, call, left, right, test);
  } else if (call === "Boolean") {
    if (argsLength === 0) {
      return new Node(ExpressionNodeType.LITERAL_BOOLEAN, false);
    }
    val = createRuntimeAst(expression, args[0]);
    return new Node(ExpressionNodeType.UNARY, call, val);
  } else if (call === "Number") {
    if (argsLength === 0) {
      return new Node(ExpressionNodeType.LITERAL_NUMBER, 0);
    }
    val = createRuntimeAst(expression, args[0]);
    return new Node(ExpressionNodeType.UNARY, call, val);
  } else if (call === "String") {
    if (argsLength === 0) {
      return new Node(ExpressionNodeType.LITERAL_STRING, "");
    }
    val = createRuntimeAst(expression, args[0]);
    return new Node(ExpressionNodeType.UNARY, call, val);
  } else if (call === "regExp") {
    return parseRegex(expression, ast);
  }

  throw new RuntimeError(`Unexpected function call "${call}".`);
}

function parseRegex(expression, ast) {
  const args = ast.arguments;
  // no arguments, return default regex
  if (args.length === 0) {
    return new Node(ExpressionNodeType.LITERAL_REGEX, new RegExp());
  }

  const pattern = createRuntimeAst(expression, args[0]);
  let exp;

  // optional flag argument supplied
  if (args.length > 1) {
    const flags = createRuntimeAst(expression, args[1]);
    if (isLiteralType(pattern) && isLiteralType(flags)) {
      try {
        exp = new RegExp(
          replaceBackslashes(String(pattern._value)),
          flags._value,
        );
      } catch (e) {
        throw new RuntimeError(e);
      }
      return new Node(ExpressionNodeType.LITERAL_REGEX, exp);
    }
    return new Node(ExpressionNodeType.REGEX, pattern, flags);
  }

  // only pattern argument supplied
  if (isLiteralType(pattern)) {
    try {
      exp = new RegExp(replaceBackslashes(String(pattern._value)));
    } catch (e) {
      throw new RuntimeError(e);
    }
    return new Node(ExpressionNodeType.LITERAL_REGEX, exp);
  }
  return new Node(ExpressionNodeType.REGEX, pattern);
}

function parseKeywordsAndVariables(ast) {
  if (isVariable(ast.name)) {
    const name = getPropertyName(ast.name);
    if (name.substr(0, 8) === "tiles3d_") {
      return new Node(ExpressionNodeType.BUILTIN_VARIABLE, name);
    }
    return new Node(ExpressionNodeType.VARIABLE, name);
  } else if (ast.name === "NaN") {
    return new Node(ExpressionNodeType.LITERAL_NUMBER, NaN);
  } else if (ast.name === "Infinity") {
    return new Node(ExpressionNodeType.LITERAL_NUMBER, Infinity);
  } else if (ast.name === "undefined") {
    return new Node(ExpressionNodeType.LITERAL_UNDEFINED, undefined);
  }

  throw new RuntimeError(`${ast.name} is not defined.`);
}

function parseMathConstant(ast) {
  const name = ast.property.name;
  if (name === "PI") {
    return new Node(ExpressionNodeType.LITERAL_NUMBER, Math.PI);
  } else if (name === "E") {
    return new Node(ExpressionNodeType.LITERAL_NUMBER, Math.E);
  }
}

function parseNumberConstant(ast) {
  const name = ast.property.name;
  if (name === "POSITIVE_INFINITY") {
    return new Node(
      ExpressionNodeType.LITERAL_NUMBER,
      Number.POSITIVE_INFINITY,
    );
  }
}

function parseMemberExpression(expression, ast) {
  if (ast.object.name === "Math") {
    return parseMathConstant(ast);
  } else if (ast.object.name === "Number") {
    return parseNumberConstant(ast);
  }

  let val;
  const obj = createRuntimeAst(expression, ast.object);
  if (ast.computed) {
    val = createRuntimeAst(expression, ast.property);
    return new Node(ExpressionNodeType.MEMBER, "brackets", obj, val);
  }

  val = new Node(ExpressionNodeType.LITERAL_STRING, ast.property.name);
  return new Node(ExpressionNodeType.MEMBER, "dot", obj, val);
}

function isLiteralType(node) {
  return node._type >= ExpressionNodeType.LITERAL_NULL;
}

function isVariable(name) {
  return name.substr(0, 4) === "czm_";
}

function getPropertyName(variable) {
  return variable.substr(4);
}

function createRuntimeAst(expression, ast) {
  let node;
  let op;
  let left;
  let right;

  if (ast.type === "Literal") {
    node = parseLiteral(ast);
  } else if (ast.type === "CallExpression") {
    node = parseCall(expression, ast);
  } else if (ast.type === "Identifier") {
    node = parseKeywordsAndVariables(ast);
  } else if (ast.type === "UnaryExpression") {
    op = ast.operator;
    const child = createRuntimeAst(expression, ast.argument);
    if (unaryOperators.indexOf(op) > -1) {
      node = new Node(ExpressionNodeType.UNARY, op, child);
    } else {
      throw new RuntimeError(`Unexpected operator "${op}".`);
    }
  } else if (ast.type === "BinaryExpression") {
    op = ast.operator;
    left = createRuntimeAst(expression, ast.left);
    right = createRuntimeAst(expression, ast.right);
    if (binaryOperators.indexOf(op) > -1) {
      node = new Node(ExpressionNodeType.BINARY, op, left, right);
    } else {
      throw new RuntimeError(`Unexpected operator "${op}".`);
    }
  } else if (ast.type === "LogicalExpression") {
    op = ast.operator;
    left = createRuntimeAst(expression, ast.left);
    right = createRuntimeAst(expression, ast.right);
    if (binaryOperators.indexOf(op) > -1) {
      node = new Node(ExpressionNodeType.BINARY, op, left, right);
    }
  } else if (ast.type === "ConditionalExpression") {
    const test = createRuntimeAst(expression, ast.test);
    left = createRuntimeAst(expression, ast.consequent);
    right = createRuntimeAst(expression, ast.alternate);
    node = new Node(ExpressionNodeType.CONDITIONAL, "?", left, right, test);
  } else if (ast.type === "MemberExpression") {
    node = parseMemberExpression(expression, ast);
  } else if (ast.type === "ArrayExpression") {
    const val = [];
    for (let i = 0; i < ast.elements.length; i++) {
      val[i] = createRuntimeAst(expression, ast.elements[i]);
    }
    node = new Node(ExpressionNodeType.ARRAY, val);
  } else if (ast.type === "Compound") {
    // empty expression or multiple expressions
    throw new RuntimeError("Provide exactly one expression.");
  } else {
    throw new RuntimeError("Cannot parse expression.");
  }

  return node;
}

function setEvaluateFunction(node) {
  if (node._type === ExpressionNodeType.CONDITIONAL) {
    node.evaluate = node._evaluateConditional;
  } else if (node._type === ExpressionNodeType.FUNCTION_CALL) {
    if (node._value === "test") {
      node.evaluate = node._evaluateRegExpTest;
    } else if (node._value === "exec") {
      node.evaluate = node._evaluateRegExpExec;
    } else if (node._value === "toString") {
      node.evaluate = node._evaluateToString;
    }
  } else if (node._type === ExpressionNodeType.UNARY) {
    if (node._value === "!") {
      node.evaluate = node._evaluateNot;
    } else if (node._value === "-") {
      node.evaluate = node._evaluateNegative;
    } else if (node._value === "+") {
      node.evaluate = node._evaluatePositive;
    } else if (node._value === "isNaN") {
      node.evaluate = node._evaluateNaN;
    } else if (node._value === "isFinite") {
      node.evaluate = node._evaluateIsFinite;
    } else if (node._value === "isExactClass") {
      node.evaluate = node._evaluateIsExactClass;
    } else if (node._value === "isClass") {
      node.evaluate = node._evaluateIsClass;
    } else if (node._value === "getExactClassName") {
      node.evaluate = node._evaluateGetExactClassName;
    } else if (node._value === "Boolean") {
      node.evaluate = node._evaluateBooleanConversion;
    } else if (node._value === "Number") {
      node.evaluate = node._evaluateNumberConversion;
    } else if (node._value === "String") {
      node.evaluate = node._evaluateStringConversion;
    } else if (defined(unaryFunctions[node._value])) {
      node.evaluate = getEvaluateUnaryFunction(node._value);
    }
  } else if (node._type === ExpressionNodeType.BINARY) {
    if (node._value === "+") {
      node.evaluate = node._evaluatePlus;
    } else if (node._value === "-") {
      node.evaluate = node._evaluateMinus;
    } else if (node._value === "*") {
      node.evaluate = node._evaluateTimes;
    } else if (node._value === "/") {
      node.evaluate = node._evaluateDivide;
    } else if (node._value === "%") {
      node.evaluate = node._evaluateMod;
    } else if (node._value === "===") {
      node.evaluate = node._evaluateEqualsStrict;
    } else if (node._value === "!==") {
      node.evaluate = node._evaluateNotEqualsStrict;
    } else if (node._value === "<") {
      node.evaluate = node._evaluateLessThan;
    } else if (node._value === "<=") {
      node.evaluate = node._evaluateLessThanOrEquals;
    } else if (node._value === ">") {
      node.evaluate = node._evaluateGreaterThan;
    } else if (node._value === ">=") {
      node.evaluate = node._evaluateGreaterThanOrEquals;
    } else if (node._value === "&&") {
      node.evaluate = node._evaluateAnd;
    } else if (node._value === "||") {
      node.evaluate = node._evaluateOr;
    } else if (node._value === "=~") {
      node.evaluate = node._evaluateRegExpMatch;
    } else if (node._value === "!~") {
      node.evaluate = node._evaluateRegExpNotMatch;
    } else if (defined(binaryFunctions[node._value])) {
      node.evaluate = getEvaluateBinaryFunction(node._value);
    }
  } else if (node._type === ExpressionNodeType.TERNARY) {
    node.evaluate = getEvaluateTernaryFunction(node._value);
  } else if (node._type === ExpressionNodeType.MEMBER) {
    if (node._value === "brackets") {
      node.evaluate = node._evaluateMemberBrackets;
    } else {
      node.evaluate = node._evaluateMemberDot;
    }
  } else if (node._type === ExpressionNodeType.ARRAY) {
    node.evaluate = node._evaluateArray;
  } else if (node._type === ExpressionNodeType.VARIABLE) {
    node.evaluate = node._evaluateVariable;
  } else if (node._type === ExpressionNodeType.VARIABLE_IN_STRING) {
    node.evaluate = node._evaluateVariableString;
  } else if (node._type === ExpressionNodeType.LITERAL_COLOR) {
    node.evaluate = node._evaluateLiteralColor;
  } else if (node._type === ExpressionNodeType.LITERAL_VECTOR) {
    node.evaluate = node._evaluateLiteralVector;
  } else if (node._type === ExpressionNodeType.LITERAL_STRING) {
    node.evaluate = node._evaluateLiteralString;
  } else if (node._type === ExpressionNodeType.REGEX) {
    node.evaluate = node._evaluateRegExp;
  } else if (node._type === ExpressionNodeType.BUILTIN_VARIABLE) {
    if (node._value === "tiles3d_tileset_time") {
      node.evaluate = evaluateTilesetTime;
    }
  } else {
    node.evaluate = node._evaluateLiteral;
  }
}

function evaluateTilesetTime(feature) {
  if (!defined(feature)) {
    return 0.0;
  }
  return feature.content.tileset.timeSinceLoad;
}

function getEvaluateUnaryFunction(call) {
  const evaluate = unaryFunctions[call];
  return function (feature) {
    const left = this._left.evaluate(feature);
    return evaluate(call, left);
  };
}

function getEvaluateBinaryFunction(call) {
  const evaluate = binaryFunctions[call];
  return function (feature) {
    const left = this._left.evaluate(feature);
    const right = this._right.evaluate(feature);
    return evaluate(call, left, right);
  };
}

function getEvaluateTernaryFunction(call) {
  const evaluate = ternaryFunctions[call];
  return function (feature) {
    const left = this._left.evaluate(feature);
    const right = this._right.evaluate(feature);
    const test = this._test.evaluate(feature);
    return evaluate(call, left, right, test);
  };
}

function getFeatureProperty(feature, name) {
  // Returns undefined if the feature is not defined or the property name is not defined for that feature
  if (defined(feature)) {
    return feature.getPropertyInherited(name);
  }
}

Node.prototype._evaluateLiteral = function () {
  return this._value;
};

Node.prototype._evaluateLiteralColor = function (feature) {
  const color = scratchColor;
  const args = this._left;
  if (this._value === "color") {
    if (!defined(args)) {
      Color.fromBytes(255, 255, 255, 255, color);
    } else if (args.length > 1) {
      Color.fromCssColorString(args[0].evaluate(feature), color);
      color.alpha = args[1].evaluate(feature);
    } else {
      Color.fromCssColorString(args[0].evaluate(feature), color);
    }
  } else if (this._value === "rgb") {
    Color.fromBytes(
      args[0].evaluate(feature),
      args[1].evaluate(feature),
      args[2].evaluate(feature),
      255,
      color,
    );
  } else if (this._value === "rgba") {
    // convert between css alpha (0 to 1) and cesium alpha (0 to 255)
    const a = args[3].evaluate(feature) * 255;
    Color.fromBytes(
      args[0].evaluate(feature),
      args[1].evaluate(feature),
      args[2].evaluate(feature),
      a,
      color,
    );
  } else if (this._value === "hsl") {
    Color.fromHsl(
      args[0].evaluate(feature),
      args[1].evaluate(feature),
      args[2].evaluate(feature),
      1.0,
      color,
    );
  } else if (this._value === "hsla") {
    Color.fromHsl(
      args[0].evaluate(feature),
      args[1].evaluate(feature),
      args[2].evaluate(feature),
      args[3].evaluate(feature),
      color,
    );
  }
  return Cartesian4.fromColor(color, scratchStorage.getCartesian4());
};

Node.prototype._evaluateLiteralVector = function (feature) {
  // Gather the components that make up the vector, which includes components from interior vectors.
  // For example vec3(1, 2, 3) or vec3(vec2(1, 2), 3) are both valid.
  //
  // If the number of components does not equal the vector's size, then a RuntimeError is thrown - with two exceptions:
  // 1. A vector may be constructed from a larger vector and drop the extra components.
  // 2. A vector may be constructed from a single component - vec3(1) will become vec3(1, 1, 1).
  //
  // Examples of invalid constructors include:
  // vec4(1, 2)        // not enough components
  // vec3(vec2(1, 2))  // not enough components
  // vec3(1, 2, 3, 4)  // too many components
  // vec2(vec4(1), 1)  // too many components

  const components = scratchStorage.getArray();
  const call = this._value;
  const args = this._left;
  const argsLength = args.length;
  for (let i = 0; i < argsLength; ++i) {
    const value = args[i].evaluate(feature);
    if (typeof value === "number") {
      components.push(value);
    } else if (value instanceof Cartesian2) {
      components.push(value.x, value.y);
    } else if (value instanceof Cartesian3) {
      components.push(value.x, value.y, value.z);
    } else if (value instanceof Cartesian4) {
      components.push(value.x, value.y, value.z, value.w);
    } else {
      throw new RuntimeError(
        `${call} argument must be a vector or number. Argument is ${value}.`,
      );
    }
  }

  const componentsLength = components.length;
  const vectorLength = parseInt(call.charAt(3));

  if (componentsLength === 0) {
    throw new RuntimeError(`Invalid ${call} constructor. No valid arguments.`);
  } else if (componentsLength < vectorLength && componentsLength > 1) {
    throw new RuntimeError(
      `Invalid ${call} constructor. Not enough arguments.`,
    );
  } else if (componentsLength > vectorLength && argsLength > 1) {
    throw new RuntimeError(`Invalid ${call} constructor. Too many arguments.`);
  }

  if (componentsLength === 1) {
    // Add the same component 3 more times
    const component = components[0];
    components.push(component, component, component);
  }

  if (call === "vec2") {
    return Cartesian2.fromArray(components, 0, scratchStorage.getCartesian2());
  } else if (call === "vec3") {
    return Cartesian3.fromArray(components, 0, scratchStorage.getCartesian3());
  } else if (call === "vec4") {
    return Cartesian4.fromArray(components, 0, scratchStorage.getCartesian4());
  }
};

Node.prototype._evaluateLiteralString = function () {
  return this._value;
};

Node.prototype._evaluateVariableString = function (feature) {
  let result = this._value;
  let match = variableRegex.exec(result);
  while (match !== null) {
    const placeholder = match[0];
    const variableName = match[1];
    let property = getFeatureProperty(feature, variableName);
    if (!defined(property)) {
      property = "";
    }
    result = result.replace(placeholder, property);
    variableRegex.lastIndex += property.length - placeholder.length;
    match = variableRegex.exec(result);
  }
  return result;
};

Node.prototype._evaluateVariable = function (feature) {
  // evaluates to undefined if the property name is not defined for that feature
  return getFeatureProperty(feature, this._value);
};

function checkFeature(ast) {
  return ast._value === "feature";
}

// PERFORMANCE_IDEA: Determine if parent property needs to be computed before runtime
Node.prototype._evaluateMemberDot = function (feature) {
  if (checkFeature(this._left)) {
    return getFeatureProperty(feature, this._right.evaluate(feature));
  }
  const property = this._left.evaluate(feature);
  if (!defined(property)) {
    return undefined;
  }

  const member = this._right.evaluate(feature);
  if (
    property instanceof Cartesian2 ||
    property instanceof Cartesian3 ||
    property instanceof Cartesian4
  ) {
    // Vector components may be accessed with .r, .g, .b, .a and implicitly with .x, .y, .z, .w
    if (member === "r") {
      return property.x;
    } else if (member === "g") {
      return property.y;
    } else if (member === "b") {
      return property.z;
    } else if (member === "a") {
      return property.w;
    }
  }
  return property[member];
};

Node.prototype._evaluateMemberBrackets = function (feature) {
  if (checkFeature(this._left)) {
    return getFeatureProperty(feature, this._right.evaluate(feature));
  }
  const property = this._left.evaluate(feature);
  if (!defined(property)) {
    return undefined;
  }

  const member = this._right.evaluate(feature);
  if (
    property instanceof Cartesian2 ||
    property instanceof Cartesian3 ||
    property instanceof Cartesian4
  ) {
    // Vector components may be accessed with [0][1][2][3], ['r']['g']['b']['a'] and implicitly with ['x']['y']['z']['w']
    // For Cartesian2 and Cartesian3 out-of-range components will just return undefined
    if (member === 0 || member === "r") {
      return property.x;
    } else if (member === 1 || member === "g") {
      return property.y;
    } else if (member === 2 || member === "b") {
      return property.z;
    } else if (member === 3 || member === "a") {
      return property.w;
    }
  }
  return property[member];
};

Node.prototype._evaluateArray = function (feature) {
  const array = [];
  for (let i = 0; i < this._value.length; i++) {
    array[i] = this._value[i].evaluate(feature);
  }
  return array;
};

// PERFORMANCE_IDEA: Have "fast path" functions that deal only with specific types
// that we can assign if we know the types before runtime

Node.prototype._evaluateNot = function (feature) {
  const left = this._left.evaluate(feature);
  if (typeof left !== "boolean") {
    throw new RuntimeError(
      `Operator "!" requires a boolean argument. Argument is ${left}.`,
    );
  }
  return !left;
};

Node.prototype._evaluateNegative = function (feature) {
  const left = this._left.evaluate(feature);
  if (left instanceof Cartesian2) {
    return Cartesian2.negate(left, scratchStorage.getCartesian2());
  } else if (left instanceof Cartesian3) {
    return Cartesian3.negate(left, scratchStorage.getCartesian3());
  } else if (left instanceof Cartesian4) {
    return Cartesian4.negate(left, scratchStorage.getCartesian4());
  } else if (typeof left === "number") {
    return -left;
  }

  throw new RuntimeError(
    `Operator "-" requires a vector or number argument. Argument is ${left}.`,
  );
};

Node.prototype._evaluatePositive = function (feature) {
  const left = this._left.evaluate(feature);

  if (
    !(
      left instanceof Cartesian2 ||
      left instanceof Cartesian3 ||
      left instanceof Cartesian4 ||
      typeof left === "number"
    )
  ) {
    throw new RuntimeError(
      `Operator "+" requires a vector or number argument. Argument is ${left}.`,
    );
  }

  return left;
};

Node.prototype._evaluateLessThan = function (feature) {
  const left = this._left.evaluate(feature);
  const right = this._right.evaluate(feature);

  if (typeof left !== "number" || typeof right !== "number") {
    throw new RuntimeError(
      `Operator "<" requires number arguments. Arguments are ${left} and ${right}.`,
    );
  }

  return left < right;
};

Node.prototype._evaluateLessThanOrEquals = function (feature) {
  const left = this._left.evaluate(feature);
  const right = this._right.evaluate(feature);

  if (typeof left !== "number" || typeof right !== "number") {
    throw new RuntimeError(
      `Operator "<=" requires number arguments. Arguments are ${left} and ${right}.`,
    );
  }

  return left <= right;
};

Node.prototype._evaluateGreaterThan = function (feature) {
  const left = this._left.evaluate(feature);
  const right = this._right.evaluate(feature);

  if (typeof left !== "number" || typeof right !== "number") {
    throw new RuntimeError(
      `Operator ">" requires number arguments. Arguments are ${left} and ${right}.`,
    );
  }

  return left > right;
};

Node.prototype._evaluateGreaterThanOrEquals = function (feature) {
  const left = this._left.evaluate(feature);
  const right = this._right.evaluate(feature);

  if (typeof left !== "number" || typeof right !== "number") {
    throw new RuntimeError(
      `Operator ">=" requires number arguments. Arguments are ${left} and ${right}.`,
    );
  }

  return left >= right;
};

Node.prototype._evaluateOr = function (feature) {
  const left = this._left.evaluate(feature);
  if (typeof left !== "boolean") {
    throw new RuntimeError(
      `Operator "||" requires boolean arguments. First argument is ${left}.`,
    );
  }

  // short circuit the expression
  if (left) {
    return true;
  }

  const right = this._right.evaluate(feature);
  if (typeof right !== "boolean") {
    throw new RuntimeError(
      `Operator "||" requires boolean arguments. Second argument is ${right}.`,
    );
  }

  return left || right;
};

Node.prototype._evaluateAnd = function (feature) {
  const left = this._left.evaluate(feature);
  if (typeof left !== "boolean") {
    throw new RuntimeError(
      `Operator "&&" requires boolean arguments. First argument is ${left}.`,
    );
  }

  // short circuit the expression
  if (!left) {
    return false;
  }

  const right = this._right.evaluate(feature);
  if (typeof right !== "boolean") {
    throw new RuntimeError(
      `Operator "&&" requires boolean arguments. Second argument is ${right}.`,
    );
  }

  return left && right;
};

Node.prototype._evaluatePlus = function (feature) {
  const left = this._left.evaluate(feature);
  const right = this._right.evaluate(feature);
  if (right instanceof Cartesian2 && left instanceof Cartesian2) {
    return Cartesian2.add(left, right, scratchStorage.getCartesian2());
  } else if (right instanceof Cartesian3 && left instanceof Cartesian3) {
    return Cartesian3.add(left, right, scratchStorage.getCartesian3());
  } else if (right instanceof Cartesian4 && left instanceof Cartesian4) {
    return Cartesian4.add(left, right, scratchStorage.getCartesian4());
  } else if (typeof left === "string" || typeof right === "string") {
    // If only one argument is a string the other argument calls its toString function.
    return left + right;
  } else if (typeof left === "number" && typeof right === "number") {
    return left + right;
  }

  throw new RuntimeError(
    `Operator "+" requires vector or number arguments of matching types, or at least one string argument. Arguments are ${left} and ${right}.`,
  );
};

Node.prototype._evaluateMinus = function (feature) {
  const left = this._left.evaluate(feature);
  const right = this._right.evaluate(feature);
  if (right instanceof Cartesian2 && left instanceof Cartesian2) {
    return Cartesian2.subtract(left, right, scratchStorage.getCartesian2());
  } else if (right instanceof Cartesian3 && left instanceof Cartesian3) {
    return Cartesian3.subtract(left, right, scratchStorage.getCartesian3());
  } else if (right instanceof Cartesian4 && left instanceof Cartesian4) {
    return Cartesian4.subtract(left, right, scratchStorage.getCartesian4());
  } else if (typeof left === "number" && typeof right === "number") {
    return left - right;
  }

  throw new RuntimeError(
    `Operator "-" requires vector or number arguments of matching types. Arguments are ${left} and ${right}.`,
  );
};

Node.prototype._evaluateTimes = function (feature) {
  const left = this._left.evaluate(feature);
  const right = this._right.evaluate(feature);
  i