/** 操作符重载，使用自定义解释器实现操作符重载 */
public static void operatorOverload() {
/*
* 扩展Fel的+运算符，使其支持数组+数组
*/
FelEngine fel = getEngine();
// 单价
double[] price = new double[] {2, 3, 4};
// 费用
double[] cost = new double[] {0.3, 0.3, 0.4};
FelContext ctx = fel.getContext();
ctx.set("单价", price);
ctx.set("费用", cost);
String exp = "单价+费用";
Interpreters interpreters = new Interpreters();
// 定义"+"操作符的解释方法。
interpreters.add(
"+",
new Interpreter() {
@Override
public Object interpret(FelContext context, FelNode node) {
List<FelNode> args = node.getChildren();
double[] leftArg = (double[]) args.get(0).eval(context);
double[] rightArg = (double[]) args.get(1).eval(context);
return sum(leftArg) + sum(rightArg);
}
// 对数组进行求和
public double sum(double[] array) {
double d = 0;
for (int i = 0; i < array.length; i++) {
d += array[i];
}
return d;
}
});
// 使用自定义解释器作为编译选项进行进行编译
Expression expObj = fel.compile(exp, null, interpreters);
Object eval = expObj.eval(ctx);
System.out.println("数组相加:" + eval);
}
/** 大数据量计算（计算1千万次) */
public static void massData() {
FelEngine fel = getEngine();
final Interpreters opti = new Interpreters();
final MutableInt index = new MutableInt(0);
int count = 10 * 1000 * 1000;
final double[] counts = new double[count];
final double[] prices = new double[count];
Arrays.fill(counts, 10d);
Arrays.fill(prices, 2.5d);
opti.add(
"单价",
new Interpreter() {
@Override
public Object interpret(FelContext context, FelNode node) {
return prices[index.intValue()];
}
});
opti.add(
"数量",
new Interpreter() {
@Override
public Object interpret(FelContext context, FelNode node) {
return counts[index.intValue()];
}
});
Expression expObj = fel.compile("单价*数量", null, opti);
long start = System.currentTimeMillis();
Object result = null;
for (int i = 0; i < count; i++) {
result = expObj.eval((FelContext) null);
index.increment();
}
long end = System.currentTimeMillis();
System.out.println("大数据量计算:" + result + ";耗时:" + (end - start));
}