SuperBASIC function for type validation

[grafvonb]

I can't find it . How to check if a non-numeric of empty data has been entered in a numeric field (or vice versa) using SuperBASIC?

[Artificer]

Hi,

Are you looking for a function/procedure in Superbasic to ensure only numeric input? If so there are a few examples in QL World Magazine.

In QLWorld 1986 November 1986 page 36 there is a Superbasic function. The magazine can be downloaded from Dilwyn Jones site here http://www.dilwyn.me.uk/mags/qluserworl ... 986-11.pdf

There was also a calculator project later on perhaps in 1988.

Cheers

[tofro]

There are quite some ways to skin that cat:

The S*Basic reference manual has another nice example of a "safe input" routine in its INPUT section that doesn't need any Toolkit.

With some "modern" toolkits/compilers you can make this significantly simpler.

WHEN ERROR: Catch the "bad parameter" error on coercion and repeat input

DIY Toolkit has some functions (CHECKF and CHECK%) that test whether a string can safely be converted to a number.

Turbo Toolkit has functions EDITF and EDIT%, which will reject anything that is not a proper number.

[NormanDunbar]

Code: Select all

1000 WHEN ERRor
1010    PRINT "That was not a number!"
1020    CONTINUE
1030 END WHEN
1040 :
1050 :
2000 REPeat loop
2010    INPUT "Please enter a number: "; num$
2020    num = num$
2030    PRINT "Your number was: " & num
2040 END REPeat loop

The above sort of works. Empty strings or anything not starting with a digit cause the error handler to fire up and tell you off. It converts anything that starts with a digit to a number up until the first non-digit character. "123x" will return the value 123 and not cause an error.

Number formats such as "1e6" don't fire the error handler, but return 1e6 as the value. Floating point numbers are happily accepted as well.

HTH

Cheers,
Norm.

[NormanDunbar]

Beaten, once again, by tofro.

[tofro]

Beaten, once again, by tofro.

No worries, Norm, I'll hold back next time

At least you've presented an example that works in SBASIC - I haven't.

Tobias

[NormanDunbar]

Nah, don't hold back, I have been known to be wrong! Just ask my wife!

Cheers,
Norm.

[grafvonb]

Many thanks guys, I have now a lot of stuff to check!

[pjw]

Ive never been fond of WHEN ERRor. I just use it as a last resort. Perhaps this is because of all the problems the various implementation had in their early incarnations. But even now there are tricky issues to beware of. Viz:

Code: Select all

1000 WHEN ERRor
1010    PRINT "That was not a number!"
1020    CONTINUE
1030 END WHEN
1040 :
1050 :
2000 REPeat loop
2010    INPUT "Please enter a number: "; num$
2015    IF num$ = '': EXIT loop
2020    num = num$
2030    PRINT "Your number was: " & num
2040 END REPeat loop
2050 :
2060 num = 5/0: REMark Just a trivial example

The problem being demonstrated is that the next error encountered will (probably unintentionally) trip the same WHEN ERRor clause. Ones needs to remember to turn WHEN ERRor off:

Code: Select all

1000 WHEN ERRor
1010    PRINT "That was not a number!"
1020    CONTINUE
1030 END WHEN
1040 :
1050 :
2000 REPeat loop
2010    INPUT "Please enter a number: "; num$
2015    IF num$ = '': EXIT loop
2020    num = num$
2030    PRINT "Your number was: " & num
2040 END REPeat loop
2050 :
2052 :
2055 WHEN ERRor
2057 END WHEN: REMark WHEN ERR turned off
2058 :
2060 num = 5/0

[NormanDunbar]

Hi Per,

good point, well made. Thanks.


Cheers,
Norm.