/** 自定义 解释器 */
public static void userInterpreter() {
FelEngine fel = getEngine();
String costStr = "成本";
FelContext rootContext = fel.getContext();
rootContext.set(costStr, "60000");
FelNode node = fel.parse(costStr);
// 将变量解析成常量
node.setInterpreter(new ConstInterpreter(rootContext, node));
System.out.println(node.eval(rootContext));
}
public static void testCompile() {
FelEngine fel = getEngine();
FelContext ctx = fel.getContext();
ctx.set("单价", 5000);
ctx.set("数量", 12);
ctx.set("运费", 7500);
Expression exp = fel.compile("单价*数量+运费", ctx);
Object result = exp.eval(ctx);
System.out.println(result);
}
public static void testBigNumber() {
// 构建大数值计算引擎
FelEngine fel = FelBuilder.bigNumberEngine();
FelContext ctx = fel.getContext();
ctx.set("num", new BigInteger("22222222222222222222222222222222"));
String input = "111111111111111111111111111111+num";
Object value = fel.eval(input);
Object compileValue = fel.compile(input, ctx).eval(ctx);
System.out.println("大数值计算（解释执行）:" + value);
System.out.println("大数值计算（编译执行）:" + compileValue);
}
/** 多层次上下文环境(变量命名空间) */
public static void contexts() {
FelEngine fel = getEngine();
String costStr = "成本";
String priceStr = "价格";
FelContext baseCtx = fel.getContext();
// 父级上下文中设置成本和价格
baseCtx.set(costStr, 50);
baseCtx.set(priceStr, 100);
String exp = priceStr + "-" + costStr;
Object baseCost = fel.eval(exp);
System.out.println("期望利润：" + baseCost);
FelContext ctx = new ContextChain(baseCtx, new MapContext());
// 通货膨胀导致成本增加（子级上下文 中设置成本，会覆盖父级上下文中的成本）
ctx.set(costStr, 50 + 20);
Object allCost = fel.eval(exp, ctx);
System.out.println("实际利润：" + allCost);
}
/** 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);
}
