=====Emulating the C assignment function=====

//by Richard Russell, July 2009//\\ \\  In the **C** programming language, an //assignment// operation such as:\\ \\ 
<code c>
        variable = expression
</code>
can be used either as a //statement// or as a //function//. When used as a function, it returns the new value of the variable. Whilst at first sight this might not seem very useful, it is particularly convenient in the case of a **while** loop, for example:\\ \\ 
<code c>
        while (variable = expression)
          {
            // Do something useful here
          }
</code>
Here **variable** is set equal to the value of **expression** and if its new value is //non-zero// the body of the loop is executed (note that it is //not// testing whether **variable** is equal to **expression**; in **C** you do that using the == operator).\\ \\  Since in BBC BASIC an assignment is a //statement//, you can't straightforwardly do this, and you have to code it as follows:\\ \\ 
<code bb4w>
        variable = expression
        WHILE variable
          REM Do something useful here
          variable = expression
        ENDWHILE
</code>
As you can see, this involves writing the assignment statement **twice**, once outside the loop and again inside the loop. This is inelegant and potentially error-prone, for example you might make a change to one of the assignments but forget to change the other.\\ \\  To emulate the **C** behaviour you can utilise this simple function:\\ \\ 
<code bb4w>
        DEF FNassign(RETURN variable, expression)
        variable = expression
        = variable
</code>
Now you can write the loop as follows:\\ \\ 
<code bb4w>
        WHILE FNassign(variable, expression)
          REM Do something useful here
        ENDWHILE
</code>
Note that since **variant** numeric variables are used in the function (i.e. without a 'type' suffix character) it will work equally well with **integer** variables and values as with **floating-point** variables.