Generator/Exponential: Difference between revisions

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 * http://en.wikipedia.org/wiki/Generator_(computer_science)
-'''Task:''' Write a generator (or generators), in the most natural way in your language, that produces the numbers that are squares (<math>n^2</math>) but not cubes (<math>m^3</math>) and use that to print the first 20 members of that sequence.
+'''Task:''' Write a generator (or generators), in the most natural way in your language, that produces the numbers that are squares (<math>n^2</math>) but not cubes (<math>m^3</math>) and use that to print the first 21st to 30th members of that sequence.
+=={{header|Tcl}}==
+{{works with|Tcl|8.6}
+<lang tcl>package require Tcl 8.6
+proc powers m {
+    yield
+    for {set n 0} true {incr n} {
+	yield [expr {$n ** $m}]
+    }
+}
+coroutine squares powers 2
+coroutine cubes powers 3
+coroutine filtered apply {{s1 s2} {
+    yield
+    set f [$s2]
+    set v [$s1]
+    while true {
+	if {$v > $f} {
+	    set f [$s2]
+	    continue
+	} elseif {$v < $f} {
+	    yield $v
+	}
+	set v [$s1]
+    }
+}} squares cubes
+for {set i 0} {$i<20} {incr i} {filtered}
+for {} {$i<30} {incr i} {
+    puts [filtered]
+}</lang>
+Output:
+<pre>
+</pre>