eval function

Overview

eval is used to execute the code on the fly. The string has an eval method and directly to call it as below.

"System.println(100);".eval();

The eval’s arguments are assigned to $$ like command line arguments as an array.

"System.println($$.sum());".eval(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);    // => 55

Examples

Example 1. Normal case

Code

var code = 'System.println("hello, world");';
code.eval();

Result

hello, world

Example 2. Multiple lines

Code

var code = %{
    using DateTime;
    var dt = new DateTime("2020/12/24");
    System.println(dt.toString());
};
code.eval();

Result

2020/12/24 00:00:00

Example 3. Exception in eval

Code

var code = %{
    function evalFunction() {
        try {
            throw RuntimeException("Thrown from eval");
        } catch (e) {
            System.println("The message in eval");
            throw;
        }
    }
    evalFunction();
};
function mainFunction(code) {
    code.eval();
}

try {
    mainFunction(code);
} catch (e) {
    System.println(e.type(), ": ", e.what());
    e.printStackTrace();
}

Result

The message in eval
RuntimeException: Thrown from eval
Stack Trace Information:
        at function evalFunction(<eval>:4)
        at <eval-block>(<eval>:10)
        at function mainFunction(test.kx:13)
        at <main-block>(test.kx:17)

Example 4. Arguments in eval

Code

"System.println($$.sum());".eval(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);    // => 55