[Main]
Name=FEXP
Type=Function
Subtype=Macro constructor
Header Files=timath.h
Real Definition=#define FEXP(x,y) (*(float*)&(bcd){0x4000+y,0x##x##LL<<4*(17-sizeof(#x))})
See Also=float_to_bcd, bcd_to_float, bcd_var

[Description]
A deprecated macro used to define floating point numbers.

[Explanation]
Yet one deprecated macro. <CODE>FEXP(<I>m</I>,<I>e</I>)</CODE> constructs
a number <CODE><I>m</I>*10^<I>e</I></CODE> where <I>m</I> is a sequence
of digits (without decimal point) which is assumed to represent decimal number
<I>m.mmmm...</I>, e.g. <CODE>FEXP(2514,5)</CODE> represents number
<CODE>2.514*10^5</CODE> (<CODE>251400</CODE> or <CODE>2.514e5</CODE> using
conventional exponential notation), and <CODE>FEXP(42,-3)</CODE> represents
number <CODE>4.2*10^-3</CODE> (<CODE>0.0042</CODE> or <CODE>4.2e-3</CODE>).
<CODE>FEXP(1,3)</CODE> is <CODE>1*10^3</CODE> (<CODE>1000</CODE> or <CODE>1e3</CODE>).
<I>mantissa</I> must be the constant sequence of digits, without leading zeros,
but the way on which <CODE>FEXP</CODE> is implemented allows that
<I>exponent</I> may be a variable or an expression, like
<CODE>FEXP(314,a)</CODE>, when even <I>mantissa</I> is not a constant, you
can use function <A HREF="$$LINK(ldexp10)">ldexp10</A>. Anyway, you don't need to
use <CODE>FEXP</CODE> any more: simply use conventional exponential notation.
E.g. simply use <CODE>4.2e3</CODE> instead of <CODE>FEXP(42,3)</CODE> etc.
<BR><BR>
Note that <CODE>a&nbsp;=&nbsp;FEXP(<I>m</I>,<I>e</I>)</CODE> is not the same as
<CODE>bcd_var(a).exponent&nbsp;=&nbsp;<I>e</I>+0x4000</CODE>
and <CODE>bcd_var(a).mantissa&nbsp;=&nbsp;<I>m</I></CODE>. The first part is
true; the second is not. More precise, <CODE>FEXP</CODE> shifts <I>m</I> to
the left enough number of times to produce correct normalized mantissa (see
<A HREF="$$LINK(bcd)">bcd</A> for more info).
So, when you type <CODE>a&nbsp;=&nbsp;FEXP(352,3)</CODE> it works like
<CODE>bcd_var(a).exponent&nbsp;=&nbsp;0x4003</CODE>
and <CODE>bcd_var(a).mantissa&nbsp;=&nbsp;0x3520000000000000</CODE>.
For more description about internal format of
floating point numbers, see <A HREF="$$LINK(bcd)">bcd</A>.
