Step 3: Add the corresponding digits of the strings.
At
first glance. vou
might
assume
that
A$
and B$ can
now
be
added using the following statement:
C$=A$+B$
This
is
incorrect. When strings are added
with
a plus sign they are not added.
but are concatenated:
C$=A$+B$
C$=
[112131415161718IgI0111213/415161
+
1~]~I~I~!~M~I~Th17J914[3151*1
C$=
111213/41516/718Ig/0
/112j31415161~1~1~1~1~1~1~1~15171*1*1*1
We
want
to
add the
digits
in the strings.
not
concatenate the strings. To add
the contents of numeric strings. each digit must be extracted separately
from the string. converted into a numeric digit. then added to
one
digit from
the
other string. This
is
done
with
a routine using the
two
string functions
VAL
and MID$.
1020
FOR
I=LEN(A$)
TO
1
8TEP-l
1030
A=VAL(MID$(A$,I,l»
1050
B=VAL(MID$(B$,I,l»
11
f10
NE:X:T
1
where: A =
digit
extracted from
A$
B =
digit
extracted from
B$
''1''
is
a counter initialized
to
the length of the INPUT strings (either
A$
or B$
may
be
usedl.
With
each
FOR
...
NEXT loop iteration. the value of 1
is
decre-
mented by
1.
As 1decrements. it allows the string contents to
be
extracted one by
one. right
to
leH.
using the
MID$
function:
1
MID$(B$.1.1)
16
~~~~~~~~5794357~
15
~~~~~~~~579435.2
14
~~~~~~~~57943.72
13
~~~~~~~~5794.572
12
~~~~~~~~579.3572
11
~~~~~~~~57~43572
10
~~~~~~~~5.943572
9
~~~~~~~~.7943572
8
~~~~~~~.57943572
7
~~~~~~.~57943572
6
~~~~~.~~57943572
5
~~~~.~~~57943572
4
~~~.~~~~57943572
3
~~.~~~~~57943572
2
~.~~~~~~57943572
1
~~~~~~~~57943572
792
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