さっくりTclのジェネレーターについて調べたので載せておく。
比較用にjsとVBもね。

以外に日本語資料がなかったから困った。

出力

Tcl

proc gen {} {
	yield [info coroutine]
	for {set i 0} {true} {incr i} {
		yield $i
	}
}
coroutine g gen

puts [g]
puts [g]
puts [g]
puts [g]
puts [g]
puts [g]
puts [g]
puts [g]
puts [g]
puts [g]
puts [g]

JavaScript

function* gen(){

	for(let i=0;;i++){
		yield i;
	}
}
const g=gen();

console.log(g.next().value);
console.log(g.next().value);
console.log(g.next().value);
console.log(g.next().value);
console.log(g.next().value);
console.log(g.next().value);
console.log(g.next().value);
console.log(g.next().value);
console.log(g.next().value);
console.log(g.next().value);
console.log(g.next().value);

VB.Net

Imports System
Imports System.Console
Imports System.Collections.Generic

Module Program
	Iterator Function gen() As IEnumerator(Of Integer)
		For i As Integer=0 To Int32.MaxValue
			Yield i
		Next
	End Function

	Sub Main
		Dim g=gen()

		g.MoveNext() : WriteLine(g.Current)
		g.MoveNext() : WriteLine(g.Current)
		g.MoveNext() : WriteLine(g.Current)
		g.MoveNext() : WriteLine(g.Current)
		g.MoveNext() : WriteLine(g.Current)
		g.MoveNext() : WriteLine(g.Current)
		g.MoveNext() : WriteLine(g.Current)
		g.MoveNext() : WriteLine(g.Current)
		g.MoveNext() : WriteLine(g.Current)
		g.MoveNext() : WriteLine(g.Current)
		g.MoveNext() : WriteLine(g.Current)
	End Sub
End Module