- Pascal to Component Pascal translators

From: Bob Walkden <"Bob>
Date: Wed, 26 Oct 2005 08:36:46 +0100

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Chris,

> It is a relatively simple and mechanical exercise to
> translate structured IF-THEN-ELSE. WHILE, REPEAT, FOR
> statements into a form which only uses GOTOs. The converse is not.

yes, I found that out for sure. In translating a goto program into a no-goto
program there's no substitute for a brain. Some varieties of COBOL allowed
you to do strange things. We used COBOL and PLAN (an assembler) on ICL 1901T
mainframes. One of my colleagues discovered a way to GO TO a location in
working storage, where he had coded some constants in object code, so the
program could execute its own working storage. This did not lead to readable
source code, and should be considered harmful.

Interesting factoid: Dijkstra did not come up with the term 'considered
harmful' for the title of his famous paper. Niklaus Wirth did.

--
Regards,
 Bob 
> -----Original Message-----
> From: blackbox{([at]})nowhere.xy> Behalf Of CFB Software
> Sent: 26 October 2005 02:39
> To: BlackBox Mailing List
> Subject: [BlackBox] - Pascal to Component Pascal translators
> 
> Hi Bob,
> 
> There's a warning in Dijkstra's 1968 paper "Go To Statement 
> Considered Harmful" related to the paper that you referenced:
> 
> "In [2] Guiseppe Jacopini seems to have proved the (logical) 
> superfluousness of the go to statement. The exercise to 
> translate an arbitrary flow diagram more or less mechanically 
> into a jump-less one, however, is not to be recommended. Then 
> the resulting flow diagram cannot be expected to be more 
> transparent than the original one." 
> 
> It is a relatively simple and mechanical exercise to 
> translate structured IF-THEN-ELSE. WHILE, REPEAT, FOR 
> statements into a form which only uses GOTOs. The converse is not.
> 
> 
> On a lighter note, there was an amusing article proposing a 
> 'COME FROM'
> statement as a solution to the problem of GOTOs:
> 
> http://www.fortran.com/fortran/come_from.html
> 
> In a similar vein, I also like the 'IF THEN MAYBE' and 'GO SOMEWHERE'
> proposals of MAYBEBOL:
> 
> http://buffy.sighup.org.uk/hfiles/aafn.html
>  
> 
> Regards,
> Chris
> 
> Chris Burrows
> CFB Software
> http://www.cfbsoftware.com/gpcp
--- BlackBox
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Received on Wed Oct 26 2005 - 09:36:46 UTC