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Forum Index : Microcontroller and PC projects : Check if input data is integer or not (MMX V5.0504)

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AussieWombat
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Joined: 04/05/2018
Location: Australia
Posts: 21

Posted: 02:20am 07 Feb 2021

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Hi all,

I have an input statement, that has to be an integer.
If I type a word into the input, it accepts it.

I was going to use an if then statement to check if it is (NAN),

I am using

fontwidth:
Input "Width of Font? ",fwidth%
IF (fwidth% =0) then
print "not a number"
goto fontwidth
endif

but if they enter zero, that stuffs that up . Or should I add to the input statement.

Input "Width of Font?(1-255) ",fwidth%

regards
AussieWombat

Chopperp

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Joined: 03/01/2018
Location: Australia
Posts: 1097

Posted: 03:07am 07 Feb 2021

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I did a quick prog. Needs refining

fwidth% = 0
Do While fwidth% = 0
Input "Width of string ", fwidth%
Print fwidth%
Loop

Brian

ChopperP

Geoffg

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Joined: 06/06/2011
Location: Australia
Posts: 3292

Posted: 10:40am 07 Feb 2021

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Brian's code is good but three extra points:

You use "IF (fwidth% =0) then" without an ENDIF. This is why entering zero causes an error. As an aside, when you are asking for help on this forum it would be worth giving a clear description and listing the full error message rather than just saying "stuffs that up".

If the user just hits Enter at the prompt fwidth% will be unchanged. If this is not what you want it would be worth initialising fwidth% to some default value (ie, 0 as in Brian's code).

You do not need brackets around conditional tests (ie, (fwidth% =0)) but also they don't hurt. I'm guessing that you come from a C background.

Geoff

Geoff Graham - http://geoffg.net

CaptainBoing

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Joined: 07/09/2016
Location: United Kingdom
Posts: 2170

Posted: 02:18pm 07 Feb 2021

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Assuming you don't want anything but digits i.e. no decimals...

fontwidth:
Do
Input "Width of Font? ",a$
While Len(a$)<1

For n=1 to len(a$)
if instr(" 0123456789",Mid(a$,n,1)<2 then
print "not a number"
goto fontwidth
endif
next

fwidth%=val(a$)

I always like to grab data as strings and then process into whatever form I need. Minimises errors because of data mis-matches and you maintain control of everything in the string. As an aside, I avoid Input - you drop into the guts of MMBasic while it is waiting for the enter key which is "blocking" i.e. it stops your code running (interrupts, timers etc)

One of my pet likes is to convert VB functions into MMBasic. I never did IsNumeric() as I never really saw much call for it, but now... With it, you could simply have:

fontwidth:

Input "Width of Font? ",a$

If IsNumeric(a$) Then
fwidth%=val(a$)
Else
print "not a number"
goto fontwidth
EndIf

Any IsNumeric() function would be pretty much the same as the first bit of code above, but with some sanity checking and switches to allow decimals (one) etc.

Happy to do it for you and add it to the library if you would like that.

You might also like to look at this Constrain() function
Edited 2021-02-08 00:32 by CaptainBoing

Schlowski
Newbie

Joined: 26/03/2014
Location: Germany
Posts: 29

Posted: 02:37pm 07 Feb 2021

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Isn't jumping with GOTO out of a FOR-NEXT loop without proper ending the loop critical?

I would assume that this leaves some sort of unresolved FOR-information on some sort of stack or so...

CaptainBoing

Guru

Joined: 07/09/2016
Location: United Kingdom
Posts: 2170

Posted: 02:42pm 07 Feb 2021

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It is bad form, yes I agree and GoTo is seen as structured programming's arch-enemy. I wanted to make the code as "look-a-like" to the original so as not to stray too much and take away from the original query - hence following up with an example using a nice function - structure restored.

Regardless, MMBasic (at least on MM2 so I suspect all other platforms are the same as the core language hasn't been changed) is quite happy. True some languages use the stack for loops and this would as you suspect blow up memory, but not MMBasic (same with Do/Loop and Select/End Select). Internally they seem to act almost as if they are "aliases" for If/GoTo pairs, mimicking what CPUs do in the binary with test and Jump.

Try this bit of code below, just runs happily forever

Fred:

For n=1 To 1000
GoTo Fred
Next

Edited 2021-02-08 01:23 by CaptainBoing

TassyJim

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Joined: 07/08/2011
Location: Australia
Posts: 6283

Posted: 07:42pm 07 Feb 2021

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For this problem, I prefer to use INKEY$ and prevent non-numeric characters from getting entered.

This is written for the CMM2 but shouldn't need much change for any MMBasic platform.

' text input routines
' option console serial ' to stop messing up the display
CONST FALSE = 0
CONST TRUE = NOT false
'dim n$(10)
'dim config$(10,3)
DIM INTEGER tHt = MM.INFO(FONTHEIGHT), tWth = MM.INFO(FONTWIDTH)
DIM FLOAT num
'dim integer k
CLS

num = GetNum(10,10,"42")
PRINT
PRINT num

' Gets valid numeric input from user
' Parameters:
' Row, Col - location to echo input
' Initial$ - default value
FUNCTION GetNum(Col AS INTEGER, Row AS INTEGER,initial$)
LOCAL result$, Kbd$
LOCAL INTEGER Done
Result$ = initial$
Done = FALSE
DO WHILE INKEY$ <> "": LOOP 'Clear keyboard buffer

DO WHILE NOT Done
TEXT col*tWth,Row*tHt,Result$+CHR$(95)+ " ",lt,1,1
DO
Kbd$ = INKEY$
LOOP UNTIL Kbd$ <> ""

SELECT CASE Kbd$
CASE CHR$(27)
result$ = initial$
done = true
CASE "0","1","2","3","4","5","6","7","8", "9"
Result$ = Result$ + Kbd$
CASE "."
IF INSTR(Result$, ".") = 0 THEN
Result$ = Result$ + Kbd$
ELSE
PLAY TONE 440,440,100
END IF
CASE CHR$(13),CHR$(9)
Done = TRUE
CASE CHR$(8)
IF LEN(Result$) > 0 THEN
Result$ = LEFT$(Result$, LEN(Result$) - 1)
END IF
CASE ELSE
IF LEN(Kbd$) > 0 THEN
PLAY TONE 440,440,100
END IF
END SELECT
LOOP

TEXT col*tWth,Row*tHt,Result$+ " ",lt,1,1
GetNum = VAL(Result$)
END FUNCTION

END

Jim

VK7JH
MMedit

AussieWombat
Newbie

Joined: 04/05/2018
Location: Australia
Posts: 21

Posted: 06:58am 09 Feb 2021

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Thanks all for the replies,

I was just going through some old programs I had written for the Maximite and CMM1, and trying to get them to work in the MMX V5.0504

They will probably never see the light of day, but I thought it would be a good exercise.

I like the approach of TassyJim, and use the inkey$, as then interupts would not be hindered.

It was for an old font creation program, but now we can all use TassyJims FontTweak program to create fonts.

Aussiewombat

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