map and filter .. iteration

[gitperson1980]

In the map() example below.. is there a way to know or keep track of the actual number of the iteration?

package main

import (
	"fmt"
	"time"

	"github.com/antonmedv/expr"
)

type Env struct {
	Tweets []Tweet
}

// Methods defined on the struct become functions.
func (Env) Format(t time.Time) string { return t.Format(time.RFC822) }

type Tweet struct {
	Text string
	Date time.Time `expr:"timestamp"`
}

func main() {
	code := `map(filter(Tweets, {len(.Text) > 0}), {.Text +"\t"+ Format(.Date)+"\n"})`

	// We can use an empty instance of the struct as an environment.
	program, err := expr.Compile(code, expr.Env(Env{}))
	if err != nil {
		panic(err)
	}

	env := Env{
		Tweets: []Tweet{
			{"Oh My God!", time.Now()},
			{"How you doin?", time.Now()},
			{"Could I be wearing any more clothes?", time.Now()},
		},
	}

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

	fmt.Print(output)
}

[antonmedv]

Right now it’s not possible. But I gonna add something like #i variable.

[gitperson1980]

Great! Also I would like to return multi types vs just 1 type. Below you can see that I have to marshal all types to string. If I can return interface types per row in the return array from map .. that would be very good.

code := `map(filter(Tweets, {len(.Text) > 0}), {.Text +"\t"+ Format(.Date)+"\n"})`   // date is marshaled to string

//can we 
code := `map(filter(Tweets, {len(.Text) > 0}), {.Text ,  .Date)})`