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Compatibility with LB4 (Moderator: Richard Russell)

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Topic: for,next (Read 165 times)

Alincon
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Posts: 147

for,next
« Thread started on: Mar 24^th, 2017, 5:22pm »

The code below prints only one line, even though n>1.
Is the line "for n = 1 to n" not valid in LBB?

r.m.

Code:

 open fileName$ for input as #pjtTntNam
        n=0 : redim pjtTntNam$(99)
        while not (eof(#pjtTntNam))
            n = n+1
            input #pjtTntNam, pjtTntNam$(n)
        wend
    close #pjtTntNam
    sort pjtTntNam$(),1,n
    open fileName$ for output as #pjtTntNam
        for n = 1 to n
            print pjtTntNam$(n)
        next
    close #pjtTntNam

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Richard Russell
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Re: for,next
« Reply #1 on: Mar 24^th, 2017, 6:18pm »

on Mar 24^th, 2017, 5:22pm, Alincon wrote:

Is the line "for n = 1 to n" not valid in LBB?

I wouldn't say it's "not valid" but it's certainly ambiguous. Nothing in the LB or LBB documentation tells you whether the initial 'n = 1' assignment happens before or after the evaluation of the 'to' value. In LBB it happens before, so it's equivalent to writing:

Code:

    for n = 1 to 1

There are other ways of provoking different FOR..NEXT behaviors by writing ambiguous code. For example this:

Code:

    for n = 1 to 0
    next
    print n

which prints 1 in LBB but 2 in LB 4.

The moral is: if you don't want uncertain results, don't write ambiguous code!

Richard.

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