Tcl set variable by concatenate a command and string

Question

I am trying to set a variable like this

puts [lindex $bar 0]  # prints bar0
set foo $[lindex $bar 0]_someString

But printing the foo variable not getting the value in foo:

puts $foo  # prints $bar0_someString
# but I want the value in bar0_someString varialbe
# not the variable name.

Is this a syntax error? Is it a bad coding style to declare a variable? Is there a better way to do this?

slebetman · Accepted Answer · 2013-11-09 11:29:36Z

5

Remember that $x is just a shortcut for set x. So you can also do this:

set foo [set [lindex $bar 0]_someString]

edited Nov 9, 2013 at 11:29

answered Nov 8, 2013 at 8:44

slebetman

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2 Comments

Donal Fellows Over a year ago

The double quotes aren't necessary; Tcl doesn't get confused by such things.

slebetman Over a year ago

Ah.. yes. I blame it on too much bash programming :-). Edited my answer - thanks.

timrau · Accepted Answer · 2013-11-08 08:06:00Z

-1

The correct syntax should be:

set foo [expr $[lindex $bar 0]_someString]

A running example:

% set bar {a b c}
a b c
% set a_someString tttttt
tttttt
% set foo [expr $[lindex $bar 0]_someString]
tttttt
% puts $foo
tttttt

edited Nov 8, 2013 at 8:06

answered Nov 8, 2013 at 7:52

timrau

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2 Comments

Stan Over a year ago

Edited my questions, I want the value in bar0_someString varialbe, not the variable name.

Donal Fellows Over a year ago

This is an antipattern, one of the few things we really recommend not doing in Tcl. Use @slebetman's answer instead, which is both much faster and safer.

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