I'm trying to use a coroutine to iterate over a list so that I get the
index as well:

proc list_sequencer {o} {
yield
set i 0
while {$i < [llength $o]} {
yield [list $i [lindex $o $i]]
incr i
}
return -code break
}

set tl {s i m p l e}
coroutine next_element list_sequencer $tl
while {1} {
lassign [next_element] idx e
puts "$idx -> $e"
}
exit 0


When I run it I get
0 -> s
1 -> i
2 -> m
3 -> p
4 -> l
5 -> e
invoked "break" outside of a loop
while executing

but don't understand why. Any help greatly appreciated!

Simon

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Am 09.07.22 um 15:18 schrieb Christian Gollwitzer:

proc list_sequencer {o} {
    yield
    set i 0
    while {$i < [llength $o]} {
        yield [list $i [lindex $o $i]]
        incr i
    }
    yieldto return -code break -level 0
}

However, there is a strange side effect that if I run this in tkcon, the breaks terminates the tkcon. Maybe some coro guru can comment on it.

Found the error: The "exit 0" in the original code terminates tkcon,
therefore everything works as expected using this code! There is another (potential) problem only: After the "yieldto return" the coroutine still
exists and must be executed one more time in order to be destroyed. THis
might introduce memory leaks, depending on the usage.

Christan

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Am 09.07.22 um 13:44 schrieb Simon Geard:

I'm trying to use a coroutine to iterate over a list so that I get the
index as well:

proc list_sequencer {o} {
    yield
    set i 0
    while {$i < [llength $o]} {
        yield [list $i [lindex $o $i]]
        incr i
    }
    return -code break
}

set tl {s i m p l e}
coroutine next_element list_sequencer $tl
while {1} {
    lassign [next_element] idx e
    puts "$idx -> $e"
}
exit 0

When I run it I get
0 -> s
1 -> i
2 -> m
3 -> p
4 -> l
5 -> e
invoked "break" outside of a loop
    while executing

but don't understand why. Any help greatly appreciated!

I think you cannot yield an error code, that was missed out in the
original definition of yield. The manpage https://www.tcl.tk/man/tcl/TclCmd/coroutine.html recommends to use
"yieldto return", and in fact this works:

proc list_sequencer {o} {
yield
set i 0
while {$i < [llength $o]} {
yield [list $i [lindex $o $i]]
incr i
}
yieldto return -code break -level 0
}

However, there is a strange side effect that if I run this in tkcon, the
breaks terminates the tkcon. Maybe some coro guru can comment on it.


Christian

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 09/07/2022 14:18, Christian Gollwitzer wrote:

Am 09.07.22 um 13:44 schrieb Simon Geard:

I'm trying to use a coroutine to iterate over a list so that I get the
index as well:

proc list_sequencer {o} {
     yield
     set i 0
     while {$i < [llength $o]} {
         yield [list $i [lindex $o $i]]
         incr i
     }
     return -code break
}

set tl {s i m p l e}
coroutine next_element list_sequencer $tl
while {1} {
     lassign [next_element] idx e
     puts "$idx -> $e"
}
exit 0


When I run it I get
0 -> s
1 -> i
2 -> m
3 -> p
4 -> l
5 -> e
invoked "break" outside of a loop
     while executing

but don't understand why. Any help greatly appreciated!

I think you cannot yield an error code, that was missed out in the
original definition of yield. The manpage https://www.tcl.tk/man/tcl/TclCmd/coroutine.html recommends to use
"yieldto return", and in fact this works:

proc list_sequencer {o} {
    yield
    set i 0
    while {$i < [llength $o]} {
        yield [list $i [lindex $o $i]]
        incr i
    }
    yieldto return -code break -level 0
}

However, there is a strange side effect that if I run this in tkcon, the breaks terminates the tkcon. Maybe some coro guru can comment on it.

    Christian

Thank you. yieldto worked perfectly.

Simon

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)