[英]Declaring variables outside loop/IF structures in C
我是 C 语言的新手,而不是整体编程。 我想知道为什么当我在结构外的 if 语句中声明要使用的变量时,我收到的输出不正确(无论如何对于这段代码)。
这是我的代码:
#include<stdio.h>
void grossPay();
int main()
{
grossPay();
}
void grossPay()
{
int rate = 10, hours;
double tax, grosspay, netpay;
printf("Enter work hours this week: ");
scanf("%d", &hours);
grosspay = hours * rate;
if (grosspay <= 300 && grosspay > 0)
{
tax = 0.10;
netpay = grosspay - grosspay * tax;
printf("Pay for %d hours of week with $%d per hour\n", hours, rate);
printf("Gross pay: $%.2f\n", grosspay);
printf("Net pay: $%.2f\n", netpay);
}
else if (grosspay > 300 && grosspay <=1000)
{
tax = 0.15;
netpay = grosspay - grosspay * tax;
printf("Pay for %d hours of week with $%d per hour\n", hours, rate);
printf("Gross pay: $%.2f\n", grosspay);
printf("Net pay: $%.2f\n", netpay);
}
else if (grosspay > 1000)
{
tax = 0.25;
netpay = grosspay - grosspay * tax;
printf("Pay for %d hours of week with $%d per hour\n", hours, rate);
printf("Gross pay: $%.2f\n", grosspay);
printf("Net pay: $%.2f\n", netpay);
}
else
{
printf("Invalid input. Please try again.\n\n");
}
}
编辑:我放置的代码是我没有得到正确输出的“修复”。 我期望当我在整个 IF 语句之外声明 netpay 变量时,我会收到正确的输出,与上面代码的输出相同。
编辑 2:以前的版本
#include<stdio.h>
void grossPay();
int main()
{
grossPay();
}
void grossPay()
{
int rate = 10, hours;
double tax, grosspay, netpay;
printf("Enter work hours this week: ");
scanf("%d", &hours);
grosspay = hours * rate;
netpay = grosspay - grosspay * tax;
if (grosspay <= 300 && grosspay > 0)
{
tax = 0.10;
printf("Pay for %d hours of week with $%d per hour\n", hours, rate);
printf("Gross pay: $%.2f\n", grosspay);
printf("Net pay: $%.2f\n", netpay);
}
else if (grosspay > 300 && grosspay <=1000)
{
tax = 0.15;
printf("Pay for %d hours of week with $%d per hour\n", hours, rate);
printf("Gross pay: $%.2f\n", grosspay);
printf("Net pay: $%.2f\n", netpay);
}
else if (grosspay > 1000)
{
tax = 0.25;
printf("Pay for %d hours of week with $%d per hour\n", hours, rate);
printf("Gross pay: $%.2f\n", grosspay);
printf("Net pay: $%.2f\n", netpay);
}
else
{
printf("Invalid input. Please try again.\n\n");
}
}
相关代码归结为:
double tax;
netpay = grosspay - grosspay * tax;
tax = 0.10;
printf("Net pay: $%.2f\n", netpay);
这样做的问题是程序中的语句是按照您编写它们的顺序执行的(至少在函数中,除非特殊的控制流语句,例如continue
或goto
)。
因此:
tax
的局部变量,它是未初始化的。netpay
设置为grosspay - grosspay * tax
的结果。 这已经是错误的,因为tax
已经在这一点上没有定义的值,所以grosspay - grosspay * tax
将产生不确定的结果。tax
。 这对netpay
的价值没有影响。netpay
。事情以错误的顺序发生。 您需要在使用变量之前设置它们。
就像你在告诉某人:
你想知道为什么他们不读指环王。
也许您正试图消除重复代码。 由于if
块之间的差异是税率,您可以设置税率并在最后进行一次计算。
#include<stdio.h>
void grossPay();
int main()
{
grossPay();
}
void grossPay()
{
int rate = 10, hours;
double tax, grosspay, netpay;
printf("Enter work hours this week: ");
scanf("%d", &hours);
grosspay = hours * rate;
if (grosspay <= 300 && grosspay > 0)
{
tax = 0.10;
}
else if (grosspay > 300 && grosspay <=1000)
{
tax = 0.15;
}
else if (grosspay > 1000)
{
tax = 0.25;
}
else
{
printf("Invalid input. Please try again.\n\n");
return;
}
netpay = grosspay - grosspay * tax;
printf("Pay for %d hours of week with $%d per hour\n", hours, rate);
printf("Gross pay: $%.2f\n", grosspay);
printf("Net pay: $%.2f\n", netpay);
}
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