How to get output result for simple arithmetic expressions?

[Dentrax]

I know this would be a tricky to implement or may require some workaround. The question actually quite simple: With the following expression structure, how to get arithmetic result along with evaluation result?

<ARITHMATRIC EXPRESSION> <OPERATOR> <VALUE>

For example, what's best to way to return the value of foo+bar+baz = 6 with true evaluation result?

package main

import (
	"fmt"

	"github.com/antonmedv/expr"
)

func main() {
	env := map[string]interface{}{
		"foo": 1,
		"bar": 2,
		"baz": 3,
	}

	code := `foo + bar + baz > 5`

	program, err := expr.Compile(code, expr.Env(env))
	if err != nil {
		panic(err)
	}

	output, err := expr.Run(program, env)
	if err != nil {
		panic(err)
	}

	fmt.Println(output)
}

I know this is a way too open to bugs and unexpected cases, but still, any workaround or ideas here? What should I do?

[antonmedv]

I think it should be fairly easy. Use https://expr.medv.io/docs/Visitor-and-Patch

Patch an expression to return a tuple with the result and value from this:

1+2 == 3

to this:

[1+2 == 3, 1+2]

From AST:

BinaryNode{
	Regexp: nil,
	Operator: "==",
	Left: BinaryNode{
		Regexp: nil,
		Operator: "+",
		Left: IntegerNode{
			Value: 1,
		},
		Right: IntegerNode{
			Value: 2,
		},
	},
	Right: IntegerNode{
		Value: 3,
	},
}

to

ArrayNode{
	Nodes: []ast.Node{
		BinaryNode{
			Regexp: nil,
			Operator: "==",
			Left: BinaryNode{
				Regexp: nil,
				Operator: "+",
				Left: IntegerNode{
					Value: 1,
				},
				Right: IntegerNode{
					Value: 2,
				},
			},
			Right: IntegerNode{
				Value: 3,
			},
		},
		BinaryNode{
			Regexp: nil,
			Operator: "+",
			Left: IntegerNode{
				Value: 1,
			},
			Right: IntegerNode{
				Value: 2,
			},
		},
	},
}