How to Achieve the Functionality of JavaScript's `eval()` in Go?

JS eval() Equivalent in Go

Evaluations similar to JavaScript's eval() can indeed be performed in Go. This is especially useful for executing expressions within the program. Consider the following JavaScript code:

var x = 10;
var y = 20;
var a = eval("x * y") + "<br>";
var b = eval("2 + 2") + "<br>";
var c = eval("x + 17") + "<br>";

var res = a + b + c;

The result of res will be:

200
4
27

Implementation in Go

In Go, the equivalent functionality is provided by the go/types package. Here's how you can achieve the same in Go:

You'll need to define your own package using types.NewPackage and types.Scope. To define constants, use types.NewConst, providing the appropriate type information.

package main

import (
    "fmt"
    "go/types"
)

func main() {
    // Create a new package and scope.
    pkg := types.NewPackage("example", "example.com/eval")
    scope := types.NewScope(pkg, types.RelativeToPkg, "")

    // Insert constants into the package's scope.
    x := types.NewConst(scope, "x", types.Int, types.NewInt64(10))
    y := types.NewConst(scope, "y", types.Int, types.NewInt64(20))

    // Define the expressions to be evaluated.
    exprA := "x * y"
    exprB := "2 + 2"
    exprC := "x + 17"

    // Evaluate the expressions.
    results := []int64{}
    for _, expr := range []string{exprA, exprB, exprC} {
        result, err := types.Eval(expr, scope)
        if err != nil {
            panic(err)
        }
        results = append(results, result.Int64())
    }

    // Print the results.
    fmt.Println("Results:")
    for _, result := range results {
        fmt.Println(result)
    }
}

By running this Go code, you'll obtain the same results as in the JavaScript example:

200
4
27

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