Pesky semiColons?

[dunbarx]

Should have put this in the beginners section. Am I the only one on the planet who just now discovered that, given:

Code: Select all

if this then
   XYZ
else doThis ; doThat

is NOT the same as:

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if this then
   XYZ
else
   doThis
   doThat
end if

In the first snippet, only "do this" is bound by the "else" clause. "doThat" will execute no matter what, the same as if one placed that it on its very own line below the entirety of the if/then construct.

The semiColon seems to be a convenience for looking at lines of code, but it actually is two very independent lines. If such a line follows "else", it will not be part of that "else".

Craig

[SWEdeAndy]

If you replace the semicolon with a line break, do you then see why the two examples behave differently, as they should?

[stam]

Code: Select all

if this then
   XYZ
else doThis ; doThat

is NOT the same as:

Code: Select all

if this then
   XYZ
else
   doThis
   doThat
end if

I can't test right now, but I'm not sure

Code: Select all

if this then
   XYZ
else
   doThis; doThat
end if

is different from your second example.

Your first example doesn't have an end if, and LC permits the form:

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if <condition> then <action>
else <another action>

But any subsequent lines in that form are no longer part of the conditional. For me this is dangerous syntax as while convenient it can lead to errors.
I always err on the side of putting and end if tag at the end of my conditionals, and avoid the latter syntax to avoid errors...

Theoretically though, if I understood correct how ; works, this would be valid:

Code: Select all

if this then
   XYZ
else ; doThis ; doThat ; end if

This should replicate your second conditional...

[dunbarx]

Stam, SwedeAndy.

Thanks for the feedback.

I am not really astonished at anything apart from not having this bitten me earlier. After all, if a semiColon is just shorthand for a line break, then this:

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else doThis ; doThat

is the same as:

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else doThis
doThat

And now it is obvious that the "doThis" is indeed outside of the if/then construction. Makes perfect sense. I just had a bit of trouble debugging my code, where that last clause fired when I assumed it should not. I complained here too hastily.

Craig

[richmond62]

Deleted rather redundant post.

[richmond62]

I have just made a silly stack:
-

-
And the button "Button" contains this code:

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on mouseUp
   if the backGroundColor of btn "Button" is white then
      set the backGroundColor of btn "Button" to yellow; set the textColor of btn "Button" to red
   else
      set the backGroundColor of btn "Button" to white; set the textColor of btn "Button" to black
   end if
end mouseUp

And it changes BOTH values every time.

So: it can only be leaving an IF statement without an END IF that screws things up.

[dunbarx]

Richmond.

Well, correct, a semiColon is really just a convenience for "assembling and reading" code. I use it to keep similar or "linked" portions of my code in a more readable way

My original (incorrect) assumption was that a line of code that contained two or more semicolon-separated "clauses" were somehow locked into a single line of the "else" portion of an if-then construction. That is incorrect, and, looking back on it, wrongheaded.

Craig