Inline substitution

[CJason]

All,

This is kind of an odd issue...but, "fun" for all you guru's, I bet! This one has stumped me for awhile now.

I am writing a code converter (please keep that in mind...because that SHOULD limit the possible solutions). The issue I've run into is that I need to do a substitution "on the fly" within a line of code. For example (and this is VERY simplyfied):

Original Code

1: A = "HELO"
2: A = "B" + (A - "L")

This results in A = "BHEO". The "+" means "concatenate" and notice how "L" was removed (the "-") from A before the contatenation.

What would you programmatically convert line 2 into for perl? It needs to be short and to the point...if possible.

My attempt (obviously, doesn't quite work correctly):

$a = "HELO"
$a = "B" . ((index($a,"L")>=0)?substr($a,index($a,"L"),1,""):$a);

Thanks in advance!!

 

[ishnid]

This does it:

( $a = "B$a" ) =~ y/L//d;

 

[CJason]

I made that example pretty simple...as I stated...let's get a little more complex, shall we...

IF (C .EQS. ("B" + (A - "L"))) THEN C = "YES"

As you can see, I need this "substitution" to occur "inlined" with the IF comparison.

Any ideas?

 

[prex1]

ishnid's solution is easily transposed to your last requirement: I suspect however that there are more requirements, perhaps substitute a letter in place, add at the end,etc., and hopefully some limitations (only 4 uppercased letters chosen from a limited set?).
Without a full picture it's no use guessing solutions.
Even yours is inlinable:

$a='B'.(($n=index($a,'L'))>=0?substr($a,$n,1,''):'',$a);

Franco

http://www.xcalcs.com

: Online engineering calculations

http://www.megamag.it

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http://www.levitans.com

: Air bearing pads

 

[CJason]

prex1, your coding example is exactly what I needed...I believe! I'll post back if I run into any issues with it, but it's looking good so far!

One question...for anyone, I guess...why does prex1's solution work? I'm not really following the ":'',$a" part of it...but, using that and putting parenthesis around the entire thing, seems to do the trick???

 

[ishnid]

How about:

$a = 'HELO';
$c = 'BHEO';

if ( ( $a = "B$a" ) =~ y/L//d && $a eq $c ) {
   $c = 'YES';
}

 

[CJason]

ishnid, your example brings up a good point...won't your example change the value of $a? I don't want the value of $a to change in that example. AND, now that I re-look at prex1's solution, it will also change the value!?!? I guess that's a new requirement

 

[prex1]

Just use a temporary variable to not modify your original one.
I'll have to insist: set up all of your requirements (a basic ability of any programmer ) before trying any partial solution.

Franco

http://www.xcalcs.com

: Online engineering calculations

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads

 

[CJason]

prex1, for your solution, it's working great! However, I get the following warning:

"Useless use of a constant in void context at ..."

Is there some way to eliminate this warning using your solution? It's no big deal, I was just trying to clean up errors/warnings as much as possible.

Thanks in advance!

 

[prex1]

$a='B'.(($n=index($a,'L'))>=0?substr($a,$n,1,''):'',$a)[1];

but also

$a='B'.($a=~tr/L//d,$a);

The latter will replace all occurrences of 'L' in the string, the former only the first one.

Franco

http://www.xcalcs.com

: Online engineering calculations

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads