[英]Declaring variables outside loop/IF structures in C
我是 C 語言的新手,而不是整體編程。 我想知道為什么當我在結構外的 if 語句中聲明要使用的變量時,我收到的輸出不正確(無論如何對於這段代碼)。
這是我的代碼:
#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");
}
}
編輯:我放置的代碼是我沒有得到正確輸出的“修復”。 我期望當我在整個 IF 語句之外聲明 netpay 變量時,我會收到正確的輸出,與上面代碼的輸出相同。
編輯 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");
}
}
相關代碼歸結為:
double tax;
netpay = grosspay - grosspay * tax;
tax = 0.10;
printf("Net pay: $%.2f\n", netpay);
這樣做的問題是程序中的語句是按照您編寫它們的順序執行的(至少在函數中,除非特殊的控制流語句,例如continue
或goto
)。
因此:
tax
的局部變量,它是未初始化的。netpay
設置為grosspay - grosspay * tax
的結果。 這已經是錯誤的,因為tax
已經在這一點上沒有定義的值,所以grosspay - grosspay * tax
將產生不確定的結果。tax
。 這對netpay
的價值沒有影響。netpay
。事情以錯誤的順序發生。 您需要在使用變量之前設置它們。
就像你在告訴某人:
你想知道為什么他們不讀指環王。
也許您正試圖消除重復代碼。 由於if
塊之間的差異是稅率,您可以設置稅率並在最后進行一次計算。
#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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