1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
|
/*
* Polynomial represented using linked list, with free coefficient at last.
* This is free and unencumbered software released into the public domain.
*/
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include "construct.h"
#define COEFF_MOD 42
/*
* Add addition to the coefficient of power n of poly if it already exists.
* Return the mutated polynomial on success and NULL otherwise.
*/
construct *add_term(construct *poly, double addition, size_t n)
{
double *term = nth(poly, length(poly) - n - 1);
if (term == NULL)
return NULL;
*term += addition;
return poly;
}
/* Remove the nth term and return the mutated polynomial. */
construct *remove_term(construct *poly, size_t n)
{
if (poly == NULL)
return NULL;
size_t len = length(poly);
if (++n == len) {
construct *rest = cdr(poly);
free(car(poly));
free(poly);
return rest;
}
double *term = nth(poly, len - n);
if (term == NULL)
return poly;
*term = 0;
return poly;
}
/* Evaluate the polynomial poly of the length len at the specified value. */
double polyval(construct *poly, double value, size_t len)
{
if (!len--)
return 0;
double coeff = *(double *) car(poly);
return pow(value, len) * coeff + polyval(cdr(poly), value, len);
}
/* Print the polynomial poly of the length len using the specified varname. */
void polyprint(construct *poly, char *varname, size_t len)
{
if (len--) {
printf(len ? "%g%s^%zu + " : "%g",
*(double *) car(poly), varname, len);
polyprint(cdr(poly), varname, len);
} else {
putchar(10);
}
}
int main()
{
construct *polynomial = NULL;
srand(time(NULL));
int len = rand() % 4 + 3;
for (int i = 0; i < len; ++i) {
double *coeff = malloc(sizeof(double));
*coeff = rand() % COEFF_MOD;
polynomial = cons(coeff, polynomial);
}
puts("Initial polynomial:");
polyprint(polynomial, "x", len);
double x = rand() % COEFF_MOD;
int n = rand() % len;
polynomial = add_term(polynomial, x, n);
printf("The polynomial after adding %g to the number %d term:\n", x, n);
polyprint(polynomial, "x", len);
polynomial = remove_term(polynomial, --len);
printf("The polynomial after removing the number %d term:\n", len);
polyprint(polynomial, "x", len);
n = rand() % (len - 1);
polynomial = remove_term(polynomial, n);
printf("The polynomial after removing the number %d term:\n", n);
polyprint(polynomial, "x", len);
puts("Evaluation of the polynomial using x from stdin:");
scanf("%lf", &x);
printf("%g\n", polyval(polynomial, x, len));
return 0;
}
|
