<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> </head> <body bgcolor="#ffffff" text="#000000"> G'day everyone, I'm summing two negative floats: <blockquote> <pre>char * lhs = "-2234.6016114467412141"; char * rhs = "-4939600281397002.2812";</pre> </blockquote> According to Perl, using bignum and Math::BigFloat, the answer is <blockquote> <pre>-4939600281399236.8828114467412141</pre> </blockquote> However, according to GMP, using the code below, the answer is <blockquote> <pre>-4939600281399236.88281 </pre> </blockquote> Where have I gone wrong? What happened to the remaining "14467412141"? Kind regards, Bruce <blockquote>#include "stdafx.h" #include "gmp-static\gmp.h" #include <stdlib.h>         /* For _MAX_PATH definition */ #include <stdio.h> #include <malloc.h> #include <math.h> #define F(x) mpf_t x; mpf_init( x ); void main(void) {     F(f_lhs);     F(f_rhs);     F(f_res);     char * resbuff;     mp_exp_t exp;     char * lhs = "-2234.6016114467412141";     char * rhs = "-4939600281397002.2812";     int validOp = mpf_set_str( f_lhs, lhs, 10 );     validOp = mpf_set_str( f_rhs, rhs, 10 );     mpf_add( f_res, f_lhs, f_rhs );         resbuff = mpf_get_str( NULL, &exp, 10, 0, f_res );     printf( "Using mpf_add, %s + %s = %s (exp=%d)\n", lhs, rhs, resbuff, exp );         free(resbuff); } </blockquote> Sample output: <blockquote>Using mpf_add, -2234.6016114467412141 + -4939600281397002.2812 = -493960028139923688281 (exp=16) </blockquote> </body> </html>