square brackets in tcl arrays

Question

I have the following problem:

set start "input[0]"
set end   "output[0]"
set myArray($start,$end,pin) 1
set x "input[0]"
set y "output[0]"
set test [array names myArray $x,$y,pin]
puts "\n$test"

output should be:

input[0],output[0]

but output is:

{}

if I do:

set test [array names myArray *,*,pin]
puts "\n$test"

output is:

input[0],output[0]

Also, if I replace [] by {} ie.input{0},output{0} original code works.

Can someone please tell me what is happening here? How do I escape the [] brackets?

Answer 1

Well, let's look what is going on here:

set start "input[0]"

This will execute the command 0. I don't know what that does, but you propably don't want that. Either escape brackets with \ or use {} to enclose the name.

Same applies for

set end   "output[0]"
# ...
set x "input[0]"
set y "output[0]"

But it doesn't look like you have that problem.

The next thing is that you pass a glob pattern to array names:

set test [array names myArray $x,$y,pin]

Tcl uses [] in glob patterns for character choices, simmilar to regexp. So your pattern will only match input0,output0,pin. You can avoid that by passing the -exact switch to array names:

set test [array names myArray -exact $x,$y,pin]

Or you can escape the brackets again with a backslash (note that the pattern should look like input\[0\],input\[1\],pin after Tcl did all kinds of substitution.)