Divide problem

marcla

Hi!
When i divide 7845 with 36 i got 217 instead of 217,9166667 why??
I do like this:

VAR
long Time

Pub start
Time := 7845/36

and then i display time

Martin Hebel

Spin is an integer math interpreter (much like C and other languages), if you need floating point, you need to use the floating point object - FloatMath.spin.

-Martin

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SelmaWare Solutions - StampPlot GUI for controllers, XBee and Propeller Application Boards

Southern Illinois University Carbondale, Electronic Systems Technologies

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marcla

Can some one give me an exampel

Martin Hebel

Untested, but compiles....

Obj
  FP : "FloatMath"


Var
  Long val

Pub main       
  Val := fp.fdiv(7856,36)

Mike Green

Download the floating point library object from the Object Exchange. It includes a manual with examples.

Beanie2k

Martin Hebel said...
Untested, but compiles....

Obj
  FP : "FloatMath"


Var
  Long val

Pub main       
  Val := fp.fdiv(7856,36)

Wouldn't you want to make "val" a double or float (whichever fp.div returns)? Also some compilers require a decimal point for floating constants (e.g. 7856.0,36.0) or else they interpret the numbers as integers. Is spin this way as well or is it smart enough to know you mean floating point?

hippy

There isn't a double or float in Spin, but as the result is 32-bit a long can hold the returned value.

Spin isn't smart enough to know anything, it doesn't care what's in a long variable or what that may mean to the programmer, just that it is a 32-bit value. It's up to the programmer to later use that variable in a context which makes sense.

Tracy Allen

Marcia,

You might also do the problem in integer math.

VAR
long Time

Pub start
Time := 784500018/36   ' numerator times 10000, plus 18 for roundoff when divided by 36.
' display(Time/10000)  ' 217
' display(",")     ' radix
' display(Time//10000, fourDigits)  ' 217,9167

or, an alternative method that can kick out as many digits as you want...

VAR
long Time
byte digit

Pub start
Time := 7845/36   ' 217
'   display(Time)   ' integer part
'   display(",")    ' radix
repeat 23     ' this many to the right of the decimal point
  Time := (Time // 36) * 10
  digit := Time / 36
  ' display(digit, oneDigit)
digit := ((Time // 36) * 10 + 18)/36  ' round off last digit
'   display(digit, oneDigit)
' 217,916666666666666666666667   24 decimal places.

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Tracy Allen
www.emesystems.com

Martin Hebel

Beanie2k said...
Also some compilers require a decimal point for floating constants (e.g. 7856.0,36.0) or else they interpret the numbers as integers. Is spin this way as well or is it smart enough to know you mean floating point?

God catch, yes, the 36.0 and such is needed. since I answered initially, I felt obligated to follow-up, but didn't have time for a fully checked test. Sorry for the confusion.

-Martin