practical03_sol - Practical Session 3 — Solutions...

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Unformatted text preview: Practical Session 3 — Solutions Exercises 1. The modification of the code is straightforward. The largest integer for which the code returns a correct result is 34. For 35 and higher the code gives Inf , i.e. a overflow error. This oc- curs because the factorial exceeds a few times 10 38 , the largest single precision floating point number. 2. The left hand side of (2) should be used rather than the right hand side to avoid overflow in the numerator n ! and the denominator ( n- m )! . These individual terms may overflow even when the ratio is within the allowed range for single precision floating point. A suitable code is the following. / * calc_fperm.c * Program demonstrating the use of a function to calculate the * number of permutations of n objects chosen m at a time * / #include <stdio.h> float ffact(int m); float fperm(int n, int m); int main() { int n, m; float nperm; printf("Integer n? "); scanf("%d", &n); printf("Integer m? "); scanf("%d", &m); nperm = fperm(n, m); / * function call * / printf("Number of permutations = %g\n", nperm); return 0; } float fperm(int n, int m) { / * function to calculate number of permutations of m * objects chosen from n objects * / int i; float result; result=1.0; for (i = n; i >= n-m+1; i--) result * =i; return result; 1 }...
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This note was uploaded on 09/29/2009 for the course COSC 1002 taught by Professor Wheatland during the Three '09 term at University of Sydney.

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practical03_sol - Practical Session 3 — Solutions...

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