checking for specific invalid characters from a string list

[jarych]

(Example uses two FOR loops and MID$() function. )

Example of how to check for several possible invalid characters in input, if program expects to use Whole Numbers as inputs:


invalidchar$="abcdefghijlmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ,.?/-+"
flaginputqual=1   'for good input expected

INPUT "minutes, "; m$
INPUT "seconds, "; s$


rem first check m$
for i=1 to len(m$)
for j=1 to len(invalidchar$)
   if mid$(m$,i,1)=mid$(invalidchar$,j,1) then flaginputqual=0
next j
next i


rem last check s$
for i=1 to len(s$)
for j=1 to len(invalidchar$)
   if mid$(s$,i,1)=mid$(invalidchar$,j,1) then flaginputqual=0
next j
next i

print "flaginputqual variable value established as ";flaginputqual
print "0 indicates bad inputs and 1 indicates good inputs"


END


Some other possibilities for what or how to check, to include other specifications on the inputs or what to look for.

[B+]

Do you just want to check valid minutes and seconds?

if int(val(m$)) >= 0 and int(val(m$)) < 60 then valid.

Otherwise use INSTR to check for characters in a string.

[jarych]

Jun 27, 2019 13:30:44 GMT B+ said:

Do you just want to check valid minutes and seconds?

if int(val(m$)) >= 0 and int(val(m$)) < 60 then valid.

Otherwise use INSTR to check for characters in a string.

I may need to think more carefully about how to use VAL() and INT().  Problem seems that VAL is accepting letter-characters, and this is why I created code to check for the most likely non-digit characters in an input string.   I did some thinking about INSTR() but became unsure what to do with it.  Currently, my skill in thinking with INSTR() has become too weak.  I believe I can do most of what I want using the sample program presented.  Inputs are expected to be strings:  one of them for holding minutes, and another for holding seconds.

[B+]

Could check for valid, would be quicker test:

[restart]
scan
input "(Just enter to quit) Enter a number to test ";n$
if n$ ="" then end
OK$ = "1234567890"
for i = 1 to len(n$)
if instr(OK$, mid$(n$, i, 1)) = 0 then print "Number is not good." : goto [restart]
next
print "Number is good."
goto [restart]


[jarych]

B+
Key to understanding INSTR() is, remember that this looks for a POSITION number. I might be able to understand how to work with INSTR(), that is according to your example, and the JB helpfile.
Right now, I am thinking more about using VAL(), INT(), and STR$().

[B+]

Remember INSTR returns a value of 0 if it does not find a match, that means if one of the characters does not match the OK$ set, it is not valid making the input not valid. So INSTR gives us 2 kinds of information 1. position if present 2. no position means not in OK$ set.

VAL("M") = 0 which is an OK valid minute or second.

I am just saying for digits, checking what's valid is a shorter test that checking all possible invalid characters.

[jarych]

Jun 28, 2019 13:39:42 GMT B+ said:

Remember INSTR returns a value of 0 if it does not find a match, that means if one of the characters does not match the OK$ set, it is not valid making the input not valid. So INSTR gives us 2 kinds of information 1. position if present 2. no position means not in OK$ set.

VAL("M") = 0 which is an OK valid minute or second.

I am just saying for digits, checking what's valid is a shorter test that checking all possible invalid characters.

I was coming into that understanding but it took several hours.  Nice knowing that VAL() will ignore leading zero.