=====Non-integer modulo operation=====

//by Richard Russell, November 2011//

BBC BASIC, in common with several other languages (e.g. C), provides only an integer [[http://www.bbcbasic.co.uk/bbcwin/manual/bbcwin6.html#mod|MOD]] operator as standard. That is, you can pass non-integer values to MOD but they will be truncated to integers before the operation is carried out. For example:

<code bb4w>
        PRINT 678.9 MOD 123.45
</code>

prints the value **63**.

However the [[http://en.wikipedia.org/wiki/Modulo_operation|modulo]] operation is not fundamentally limited to integer values and occasionally it can be useful to have a version which will work with non-integers. In C this is provided by the **fmod** library function. An equivalent function in BBC BASIC can be implemented as follows:

<code bb4w>
        DEF FNfmod(x,y) = x - x DIV y * y
</code>

Now we can perform the following operation:

<code bb4w>
        PRINT FNfmod(678.9, 123.45)
</code>

and the value printed is **61.65**.