lambdas and namspace

[bitmaxis]

Hi, I'm new to tcl and jim, so I may have this ass backwards, but i find the lambda and namespace confusing

I have a proc in global namespace

proc scenario2 {scenario} {
set subs [subst [readFile scenarios/$scenario/config.tcl]]
puts "loaded scenario $scenario"
eval "set l "$subs
lambda {args} &l {
dict getdef $l {*}$args "undefined: $args"
}
}

i can do

set $s [scenario2 live]

and then

$s blah

to retrieve an arbitrary property from the dict - this is what i expect.

But when I put same function in namespace utils

set $s [::utils::scenario2 live]

$s blah
invalid command name "<reference..00000000000000000004>"

I found the answer to be

::utils::$s blah

but I expected the lambda to be in the global namespace or in the namespace of the caller.
If this is the normal behaviour, maybe some extra documentation would be useful as it's
not an intuitive default (for me anyway :)).

Apart from that jim is awesome!

Cheers.

[msteveb]

So you need to understand that lambda returns a local proc name (even though the proc is created in the local namespace). This is just the same as proc does.

If you want to export that name so that it can be used outside the namespace, you need to use namespace canon. For example.

#!/usr/bin/env jimsh

proc a::b {} {
    set x [lambda {} {
        return [namespace current]
    }]
    puts "in a::b, lambda is $x and returns [$x]"
    return [namespace canon $x]
}

set y [a::b]
puts "Got $y from a::b that returns [$y]"

Outputs:

in a::b, lambda is <reference.<functio>.00000000000000000000> and returns ::a
Got a::<reference.<functio>.00000000000000000000> from a::b that returns ::a

While you can use $x inside the namespace, you need to use namepace canon to return a name that can be resolved globally. Compare:

proc a::b {} {
    proc p {} {
        return [namespace current]
    }
    puts "in a::b, p returns [p]"
    return [namespace canon p]
}

set y [a::b]
puts "Got $y from a::b that returns [$y]"

Again we need to use namespace canon (or just return "a::p") because plain "p" won't resolve into the "a" namespace.

[bitmaxis]

Thanks for taking time out for that explanation, makes sense.
My only further comment is namespace canonical is not documented.

[msteveb]

No problem. Thanks for pointing that out. I'll make sure it gets documented.

[msteveb]

Although if you want to be Tcl compatible you can use [namespace current]::$x instead