I'm trying to discover the possible cause for an oddity when using the
'offset' parameter as
in the 'substr' funtion in the small script below. This sample exercise is
a miniaturization
of the same phenomenon which I noticed when creating a much larger
'series' item by reading
fixed-length records from a file one at a time and valuing
some variables with pieces of those records.
The notes at the right of the 2nd (uncommented) 'for' loop below indicate
that I get the
same results and values in the 'print' results when using 'different'
starting positions
in the series call to 'substr' which uses 'starting position' and 'length'
as its parameters.
The commented 'for' loop which appears first delivers the correct
results.....but I really need
to understand why the 2nd loop can use different position 'starting
values' in the call .......
and output the same results.....it doesn't seem 'right and proper'.
(There are (3) instances of a simulated record in the variable 'sample',
each is (38) characters long).
Thanks............ John D.
********************************************************************
Rebol[Title: "Sort dsysmst.txt to name sequence"]
substr: func [record offset len] [
copy/part at record offset len
]
sample: "0015342HORNBECK EDNA A0024667BADGER DONALD
R0035457ECONOMOU THOMAS S"
;In this for loop ....all results are as expected
;for i 1 114 38 [
;
; recnbr: substr sample i + 0 3
; regnbr: substr sample i + 3 4
; lname: substr sample i + 7 15
; fname: substr sample i + 22 15
; minit: substr sample i + 37 1
; print [recnbr regnbr lname fname minit]
;
;]
;In the for loop below ......
; zero or 1 offset gives same result
; 3 or 4 offset does NOT give same result
; 7 or 8 offset does NOT give same result
; 22 or 23 offset gives same result
; 37 or 38 offset does NOT give same result
for i 1 114 38 [
rec1: substr sample i 38
recnbr: substr rec1 0 3
regnbr: substr rec1 4 4
lname: substr rec1 8 15
fname: substr rec1 22 15
minit: substr rec1 38 1
print [recnbr regnbr lname fname minit]
]
halt
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