Ralf Hemmecke wrote:
>
> The following demonstrates a bug in the interpreter.
> OK, doesn't seem to be a bug, but still quite hard to figure out what's
> wrong.
> Program is attached.
>
> The two functions differ only in a line break after the statement
>
> n3: Z := x2;
>
> Thinking a bit about it, maybe
>
>
> n2: Z := x2; for i2 in 1..n2 repeat
> n3: Z := x2; for i3 in 1..n3 repeat x3 := x3 + 1
>
> is interpreted as
>
> n2: Z := x2; for i2 in 1..n2 repeat n3: Z := x2;
> for i3 in 1..n3 repeat x3 := x3 + 1
>
> Thus the error would be clear, since n3 is not available when the second
> loop is started.
I do not see how to relate what you wrote above to the attached
programs. The second program has
n2: Z := x2; for i2 in 1..n2 repeat n3: Z := x2;
for i3 in 1..n3 repeat x3 := x3 + 1
and while this code is wrong, meaning is clear and interpreter
faithfully follows rules.
When you write
n2: Z := x2; for i2 in 1..n2 repeat
n3: Z := x2; for i3 in 1..n3 repeat x3 := x3 + 1
then interpreter first joins the two lines and then parses it
using semicolons to separate statements. The effect is that
'for i2 in 1..n2 repeat n3: Z := x2' is recognized as one
loop and the second loop is executed after the first loop finishes.
So, use braces (or parenthesis) if you want to cram several
statements in a single line and treat them as a block.
>
> Still the error is very hard to detect if one mixes indentation with
> semicolon.
>
> So to all... be careful when you use just an indented one-line-block.
> It's not a block, but just a continuation of the previous line.
Exactly.
--
Waldek Hebisch
[email protected]
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