On Feb 18, 2013, at 8:02 PM, Lawrence Velázquez <[email protected]> wrote:
> I don't think return is behaving like you (or I) expect.
The following is somewhat academic, but some might find it instructive. And it
will almost certainly make Jeremy hate Tcl more than he already does.
The Tcl "return" command[1] takes the form
return [option value]* [result]?
- If you use "return", the proc just returns an empty string.
- If you use "return a", the proc returns "a". This is the common case.
- If you use "return a b", the proc again returns an empty string. It also
produces a dictionary containing the key/value pair "a : b"; this dictionary
can be captured by a "catch" command.
- If you use "return a b c", the proc returns "c" and produces the same
dictionary as before.
- If you use "return a b c d", the proc returns an empty string and produces
the dictionary "a : b, c : d".
- Ad nauseam. Some options, like "-code", are treated specially by Tcl.
Also note that Tcl does not evaluate expressions unless explicitly asked to.
The "if", "while", and "for" commands evaluate their conditionals (but not
their bodies); there may be other examples. Otherwise, you're on your own. (NB:
Expression evaluation is distinct from variable and command substitution.)
Now we see what compiler_is_port actually does.
> proc portconfigure::compiler_is_port {compiler} {
> return [portconfigure::compiler_port_name ${compiler}] != ""
> }
The compiler_port_name command is substituted, and its return value becomes a
key in the results dictionary with the associated value "!=". The proc *always*
returns the empty string. Similar issues would have come up with
arch_flag_supported.
The boolean expressions must be explicitly evaluated with "expr"; I committed
this in r103219.
Whoo, Tcl!
vq
[1] http://www.tcl.tk/man/tcl8.5/TclCmd/return.htm
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