README.md
1IMath
2=====
3
4Arbitrary precision integer and rational arithmetic library.
5
6IMath is an open-source ANSI C arbitrary precision integer and rational
7arithmetic library.
8
9IMath is copyright © 2002-2009 Michael J. Fromberger.
10
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17>
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20>
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27> SOFTWARE.
28
29
30About IMath
31-----------
32
33IMath is a library written in portable ANSI C that allows you to perform
34arithmetic on integers and rational numbers of arbitrary precision. While many
35programming languages, including Java, Perl, and Python provide arbitrary
36precision numbers as a standard library or language feature, C does not.
37
38IMath was designed to be small, self-contained, easy to understand and use, and
39as portable as possible across various platforms. The API is simple, and the
40code should be comparatively easy to modify or extend. Simplicity and
41portability are useful goals for some applications—however, IMath does
42not attempt to break performance records. If you need the fastest possible
43implementation, you might consider some other libraries, such as GNU MP (GMP),
44MIRACL, or the bignum library from OpenSSL.
45
46Programming with IMath
47----------------------
48
49Detailed descriptions of the IMath API can be found in [doc.md](doc.md).
50However, the following is a brief synopsis of how to get started with some
51simple tasks.
52
53To do basic integer arithmetic, you must declare variables of type `mpz_t` in
54your program, and call the functions defined in `imath.h` to operate on them.
55Here is a simple example that reads one base-10 integer from the command line,
56multiplies it by another (fixed) value, and prints the result to the standard
57output in base-10 notation:
58
59 #include <stdio.h>
60 #include <stdlib.h>
61 #include "imath.h"
62
63 int main(int argc, char *argv[])
64 {
65 mpz_t a, b;
66 char *buf;
67 int len;
68
69 if(argc < 2) {
70 fprintf(stderr, "Usage: testprogram <integer>\n");
71 return 1;
72 }
73
74 /* Initialize a new zero-valued mpz_t structure */
75 mp_int_init(&a);
76
77 /* Initialize a new mpz_t with a small integer value */
78 mp_int_init_value(&b, 25101);
79
80 /* Read a string value in the specified radix */
81 mp_int_read_string(&a, 10, argv[1]);
82
83 /* Multiply the two together... */
84 mp_int_mul(&a, &b, &a);
85
86 /* Print out the result */
87 len = mp_int_string_len(&a, 10);
88 buf = calloc(len, sizeof(*buf));
89 mp_int_to_string(&a, 10, buf, len);
90 printf("result = %s\n", buf);
91 free(buf);
92
93 /* Release memory occupied by mpz_t structures when finished */
94 mp_int_clear(&b);
95 mp_int_clear(&a);
96
97 return 0;
98 }
99
100This simple example program does not do any error checking, but all the IMath
101API functions return an `mp_result` value which can be used to detect various
102problems like range errors, running out of memory, and undefined results.
103
104The IMath API also supports operations on arbitrary precision rational numbers.
105The functions for creating and manipulating rational values (type `mpq_t`) are
106defined in `imrat.h`, so that you need only include them in your project if you
107wish to.
108