CS240 Lab03   Factorial Calculation

Lab Exercise:

In this lab, we'd like you to explore the capacity and precision difference among three basic data types: int, float, double.

Write a program that reads a positive real number n from user and print out the factorial result n! in three versions: integer version, float version and double version.

Generally, n! has mathematical meaning only when n is an integer. In this lab, we extend the notation of n! to positive numbers: n!=n*(n-1)*(n-2)*(n-3)*...*(n-p) where 1=<n-p<2. Any number between (0,1) has the factorial result of 1.
For example,
4.5!=4.5*3.5*2.5*1.5=59.0625
6!=6*5*4*3*2*1=720
0.31!=1

The input can be any positive real numbers such as 0.451, 5, 20.51. You can assume the input is always valid. Only the use of getchar() is allowed to read the input. Using other functions such as atof(), scanf() will result in an automatic zero. You have to convert the characters manually to a double for further calculation.

After reading the real number, three versions of factorial function are to be called to calculate the results. The prototypes of three functions are:
int fac_int(int p)       float fac_float(float p)       double fac_double(double p)
You have to implement these three functions. Pay attention that any intermediate results in the functions above should have the same type as the argument. For example, all the intermediate results in fac_float should be float.
No overflow problem has to be considered.

After calculations, print out the results in 3 lines (integer result, float result and double result). The float result and double result should be printed out in the precision of the sixth digit after the decimal point.

You can download the skeleton of the code here.

Sample Input and Output:

lore 15 % lab03.out
5
Int: 120
Float: 120.000000
Double: 120.000000

lore 16 % lab03.out
4.5
Int: 24
Float: 59.062500
Double: 59.062500

lore 17 % lab03.out
7.4152
Int: 5040
Float: 13276.550781
Double: 13276.543216

lore 18 % lab03.out
15
Int: 2004310016
Float: 1307674279936.000000
Double: 1307674368000.000000

lore 19 % lab03.out
20
Int: -2102132736
Float: 2432902298041581568.000000
Double: 2432902008176640000.000000

lore 20 % lab03.out
50.2
Int: 0
Float: Inf
Double: 72607892116462395120975832400058450157483579696933402156340346880.000000

Turnin

When you are satisfied that your program works correctly (or you run out of time), please do the following.

1. Create a directory named lab03
2. Copy all program files (*.c and *.h) and your Makefile to the directory created in step 1.
3. Goto the parent directory of lab03 and type the following command into the terminal:

   turnin -c cs240=XXXX -p lab03 lab03

   where XXXX represents your lab section number.

   The turnin section is as follows:

   Section	Time	TA
   0201	Thursday 15:30-17:20	Dan Zhang
   0301	Friday 09:30-11:20	Suli Xi
   0401	Friday 13:30-15:20	Youhan Fang
   0501	Thursday 09:30-11:20	J. C. Chin

   Make sure turnin reports that your project was submitted for grading. You can check the files you have submitted by running the following command:

   turnin -c cs240=XXXX -v -p lab03

4. Submit often to make sure that you did not try to submit after turnin has been turned off.

Grading Breakdown