Radio Shack TRS-80 model III Owner's Manual page 110

DISK BASIC
llllitlt^^
search
for.
This function
lets
you
search
through a string to see
if
it
contains another
string.
If
it
does,
instr returns the starting
position
of the substring in
the target string;
otherwise, zero
is
returned.
Note
that
the entire substring
must be
contained in
the search string,
or zero
is
returned.
Also, note
that
instr only finds the
first
occurrence of a substring at
the position
you
specify.
Examples
In these
examples, a$
=
"Lincoln":
INSTR(A$* "INC")
returns a
value of
2.
INSTR
<A$> "12")
returns a zero.
INSTR(A$t "LINCOLNABRAHAM"
)
returns a zero.
For
a
slightly different
use of instr, look
at
INSTR (3*
"1232123"
*
"12")
which
returns 5.
Sample
Program
This
program
gets
search
and
target text
from
the
keyboard, then
locates all
occurrences of the
target text in the
search
text.
Line 90
is
just for
"show."
10
CLEAR 1000
20 CLS
30
INPUT "SEARCH TEXT"? S$
413
INPUT "TARGET TEXT'S T*
45
CLS
50
C
=
s
P
=
1
'P
=
POSITION*
C =
COUNT
60
F
=
INSTR<PfS*fTt)
70 IF
F
=
THEN 120
80
C = C
+
1
90
PRINT @0>LEFT$(S$*F-i>
+
STRING*
(
LEN(T$
)>
191
)
+
-
RIGHT* <S*>LEN<S*)-F-LEN(T*)+1>
100
P
= F
+
LEN(T$)
110 IF
P
<= LEN(S$)
-
LEN(T$)
+
1
THEN
S0
120
PRINT "FOUND "5
C5
"OCCURRENCES"
109