算术问题 [英] Arithmetic problem
问题描述
我在C中有一个非常奇怪的算术问题：
double t = 0.1;
int steps = 10;
double time_step = t /（double）步骤;
我希望time_step的输出为0.01000（我的输出）是形式％5.5f的
，而是一个非常大（且不正确）的负数
数。
任何想法？
谢谢，
Schiz
Hi,
I have a very strange arithmetic problem in C:
double t = 0.1;
int steps = 10;
double time_step = t / (double)steps;
I would expect the output of time_step to be 0.01000 (my output is of
the form %5.5f), but instead it a very large (and incorrect) negative
number.
Any ideas?
Thanks,
Schiz
推荐答案
在文章< ; e5 ********** @ geraldo.cc.utexas.edu>，
Schizoid Man< sc *** @ sf.com>写道：
In article <e5**********@geraldo.cc.utexas.edu>,
Schizoid Man <sc***@sf.com> wrote:
我在C中有一个非常奇怪的算术问题：
I have a very strange arithmetic problem in C:
向我们展示一个有问题的完整程序。
- Richard
Show us a complete program that has the problem.
-- Richard
Richard Tobin写道：
Richard Tobin wrote:
向我们展示一个完整的程序问题。
Show us a complete program that has the problem.
理查德，
这是完整的程序。谢谢。
（这是有问题的模块 - 除了步骤之外传递给这个
函数的任何值，返回一个非常奇数的数字）
#include" stdafx.h"
#include" binomialtree.h"
double treeNPV（double s，double k，double r，double v，double t，int steps）
{
double time_step，up，dn，rt，p，npv;
time_step = t /（double）（步骤）;
rt = exp（r * time_step）;
up = exp（v * sqrt（time_step） ））;
dn = 1 / up;
p =（rt-dn）/（up-dn）;
npv = 0.0;
// for（int i = 0; i< = steps; i ++）
npv = v;
返回npv;
}
主要模块：
#include" stdafx .h"
#include" binomialtree.h"
int main（无效）
{
double s，k，r，v，t;
double call_npv;
int步骤;
打印f（输入资产价格S：）;
scanf_s（"％f"& s）;
printf（"输入执行价格K） ："）;
scanf_s（"％f"，& k）;
printf（" Enter riskfree rate R："）;
scanf_s（"％f"，& r）;
printf（" Enter volatility V："）;
scanf_s（" ％f"，& v）;
printf（输入到期时间T：）;
scanf_s（"％f"，& t ）;
printf（输入步数：）;
scanf_s（"％d"，& steps）;
call_npv = treeNPV（s，k，r，v，t，steps）;
printf（" Call option NPV is：％5.5f"，call_npv）;
scanf_s（"％d"，& steps）;
返回0;
}
头文件：
// stdafx.h：包含标准系统包含文件的文件，
#pragma一次
＃定义WIN32_LEAN_AND_MEAN //从Wi中排除很少使用的东西ndows
header
#include< stdio.h>
#include< tchar.h>
// binomialtree.h
#include< stdio.h>
#include< stdlib.h>
＃ include< math.h>
#define pi 3.141592653589793238
double treeNPV（double s，double k，double r，double v，double t，int步骤）;
Hi Richard,
Here''s the complete program. Thank you.
(This is the problematic module - any of the values passed to this
function apart from steps, returns a very odd number)
#include "stdafx.h"
#include "binomialtree.h"
double treeNPV(double s, double k, double r, double v, double t, int steps)
{
double time_step, up, dn, rt, p, npv;
time_step = t / (double)(steps);
rt = exp(r*time_step);
up = exp(v*sqrt(time_step));
dn = 1/up;
p = (rt-dn)/(up-dn);
npv = 0.0;
//for (int i=0; i<=steps; i++)
npv = v;
return npv;
}
Main modules:
#include "stdafx.h"
#include "binomialtree.h"
int main(void)
{
double s, k, r, v, t;
double call_npv;
int steps;
printf("Enter asset price S: ");
scanf_s("%f", &s);
printf("Enter strike price K: ");
scanf_s("%f", &k);
printf("Enter riskfree rate R: ");
scanf_s("%f", &r);
printf("Enter volatility V: ");
scanf_s("%f", &v);
printf("Enter time to expiry T: ");
scanf_s("%f", &t);
printf("Enter number of steps: ");
scanf_s("%d", &steps);
call_npv = treeNPV(s,k,r,v,t,steps);
printf("Call option NPV is: %5.5f", call_npv);
scanf_s("%d", &steps);
return 0;
}
Header files:
// stdafx.h : include file for standard system include files,
#pragma once
#define WIN32_LEAN_AND_MEAN // Exclude rarely-used stuff from Windows
headers
#include <stdio.h>
#include <tchar.h>
// binomialtree.h
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define pi 3.141592653589793238
double treeNPV(double s, double k, double r, double v, double t, int steps);
在文章< e5 ********** @ geraldo.cc.utexas.edu>，
Schizoid Man< sc *** @ sf.com>写道：
In article <e5**********@geraldo.cc.utexas.edu>,
Schizoid Man <sc***@sf.com> wrote:
这是完整的程序。谢谢。
scanf_s（"％f"，& s）;
我不知道scanf_s是什么。它不是标准的C函数。
#include< tchar.h>
Here''s the complete program. Thank you. scanf_s("%f", &s);
I don''t know what scanf_s is. It''s not a standard C function.
#include <tchar.h>
我不知道是什么tchar.h是。
但是如果scanf_s类似于scanf，那么你应该使用格式％lf
来读取双精度数。
- Richard
And I don''t know what tchar.h is.
But if scanf_s is like scanf, then you should be using format %lf
to read into a double.
-- Richard
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