Forum OpenACS Q&A: Re: AOLserver 4.5

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16: Re: AOLserver 4.5 (response to 1)
Posted by Jim Lynch on 07/12/06 11:00 AM 
doesn't line 49 need to read:

if { ![string equal $tcl_platform(platform) unix] } {
   ^                                              ^
(the arrows point at my additions)
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17: Re: Re: AOLserver 4.5 (response to 16)
Posted by Steve Manning on 07/12/06 01:57 PM
No, the extra braces are superfluous. The

    if ![tcl command] {
        do something
    }

format will work just fine.

  - Steve

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18: Tcl curly braces (response to 17)
Posted by Andrew Piskorski on 07/13/06 07:18 PM
No, the extra braces are not quite superfluous. Yes, Steve is correct that the above example will give exactly the same result regardless of whether you put braces are the argument to the "if" command or not.

But that does not mean that the braces are superfluous. Using the curly braces avoids an extra trip throught the Tcl evaluator.

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19: Re: Tcl curly braces (response to 18)
Posted by Gustaf Neumann on 07/14/06 03:06 AM
andrew, let me add to your argument:
... and with the braces, "if" and "expr" can be byte-compiled and be much faster executed (sometimes an order of magnitude). In earlier versions of Tcl (before 8.0), the braces were indeed not needed, but now they are recommended. Unfortunately, there is still much code in 7.* fashion. If you are interested, here is a script that fixes many of such occurrences in current openacs: http://media.wu-wien.ac.at/download/normalize_expressions.tcl

see as well
http://www.openacs.org/forums/message-view?message_id=335900