Chapter 2, Problem 2.90HW

You have been assigned the task of writing a C function to compute.a floating-point representation of 2^X. You decide that the best way to do this is to directly construct the IEEE single-precision representation of the result. When x is too small, your routine will return 0.0. When x is too large, it will return +∞. Fill in the blank portions of the code that follows to compute the correct result. Assume the function u2f returns a floating-point value having an identical bit representation as its unsigned argument.

Float fpwr2(int x)

{

/* Result exponent and fraction */

unsigned exp, frac;

unsigned u;

if (x <____________) {

/* Too small. Return 0.0 */

exp = _________;

frac = _________;

} else if (x < _______) {

/* Denormalized result */

exp = _________;

frac = _________;

} else if (x < _______) {

/* Normalized result. */

exp = _________;

frac = _________;

} else {

/* Too big. Return +∞ */

exp = _________;

frac = _________;

}

/* Pack exp and frac into ,32 bits */

u = exp << 23 | frac;

/* Return as float */

Return u2f (u);

}