about doulbe subsititution

[jiankunx]

I remembered somewhre in the forum about double substitution , but could not find it. Here is my problm,

I used a global variable to store variable names which I will use in a function.but I have problem to get the value of the variable.

set a1 1
set a2 2
set var(0) a1
set var(1) a2

proc printvar {varNum} {

global var

puts "$$var($varNum)"

}

when I ran "printvar 0", it prints "$a1" instread of 1. How should I solve this problem.

Thanks

 

[marsd]

Two ways:
Globally:
proc printvar {varNum} {
global var
puts "$var($varNum)"
}

Upvar:
proc printvar {n varNum} {
upvar #0 $n loc
puts $loc($varNum)
}

String tricks won't work with tcl arrays they need to
be explicitly introduced at stack level 'n'.

What you meant to do:

proc printvar {n nx} {
uplevel #0 "puts [subst -novariable $$n]($nx)"
}