I recently encountered a problem implementing an undo function in a script. I
needed to compare two arrays to see if any values had changed, like this:
put (tArray1 <> tArray2) into sDirtyFlag
so that sDirtyFlag would be true when the arrays failed to match. However,
sDirtyFlag was always false! No matter what!
I put the two arrays into globals and compared them in the message box, like
this:
put (gArray1 = gArray2), and the result was always correct. I thought there was
some hidden horrible error in my script that dementia prevented me from seeing,
until I realized that in my script I was using "<>" not "=" to compare.
See if the following script, pasted into a button, mystifies you the way it did
me. If you comment out the line:
put "xx" into tTestA2["low2"]
so that the arrays ARE equal you might see, as I did, that the comparison is
correct.
Evidently in LiveCode 4.5.3, buildnumber 1444, on MacOS 10.6.8,
"(tTestA1 <> tTestA2)" is not the same as "not(tTestA1 = tTestA2)" when the
arrays are unequal.
(I apologize that the example is so elaborate, I was attempting to reproduce
the error environment.)
tereza
-- mind the linewraps
------------------------------
on mouseUp
DoArrayComparison
end mouseUp
on DoArrayComparison
-- create 1 array
repeat for each item iii in "low1,low2,low3"
repeat for each item ii in "lower1,lower2,lower3"
repeat for each item i in "lowest1,lowest2,lowest3"
put "data" && iii && ii && i into tA1[iii][ii][i]
end repeat
end repeat
end repeat
-- create 2 arrays from it
put tA1 into tTestA1
put tTestA1 into tTestA2
-- make them unequal
put "xx" into tTestA2["low2"]
-- do three comparisons
put "(tTestA1 = tTestA2)="& (tTestA1 = tTestA2) &cr& \
"(tTestA1 <> tTestA2)="& (tTestA1 <> tTestA2) &cr& \
"not(tTestA1 = tTestA2)="& not(tTestA1 = tTestA2)
end DoArrayComparison
-------------------------------
--
Tereza Snyder
Califex Software, Inc.
<www.califexsoftware.com>
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