菜鸟求问：用if单分支选择语句替换switch语句？if...else呢？
主要是关于default情况的处理，代码如下：
/* Fig. 4.7: fig04_07.cswitch c
Counting letter grades */
#include <stdio.h>
/* function main begins program execution */
int main( void )
{
int grade; /* one grade */
int aCount = 0; /* number of As */
int bCount = 0; /* number of Bs */
int cCount = 0; /* number of Cs */
int dCount = 0; /* number of Ds */
int fCount = 0; /* number of Fs */
printf( "Enter the letter grades.\n" );
printf( "Enter the EOF character to end input.\n" );
/* loop until user types end-of-file key sequence */
while ( ( grade = getchar() ) != EOF ) {
/* determine which grade was input */
switch ( grade ) { /* switch nested in while */
case 'A': /* grade was uppercase A */
case 'a': /* or lowercase a */
++aCount; /* increment aCount */
break; /* necessary to exit switch */
case 'B': /* grade was uppercase B */
case 'b': /* or lowercase b */
++bCount; /* increment bCount */
break; /* exit switch */
case 'C': /* grade was uppercase C */
case 'c': /* or lowercase c */
++cCount; /* increment cCount */
break; /* exit switch */
case 'D': /* grade was uppercase D */
case 'd': /* or lowercase d */
++dCount; /* increment dCount */
break; /* exit switch */
case 'F': /* grade was uppercase F */
case 'f': /* or lowercase f */
++fCount; /* increment fCount */
break; /* exit switch */
case '\n': /* ignore newlines, */
case '\t': /* tabs, */
case ' ': /* and spaces in input */
break; /* exit switch */
default: /* catch all other characters */
printf( "Incorrect letter grade entered." );
printf( " Enter a new grade.\n" );
break; /* optional; will exit switch anyway */
} /* end switch */
} /* end while */
/* output summary of results */
printf( "\nTotals for each letter grade are:\n" );
printf( "A: %d\n", aCount ); /* display number of A grades */
printf( "B: %d\n", bCount ); /* display number of B grades */
printf( "C: %d\n", cCount ); /* display number of C grades */
printf( "D: %d\n", dCount ); /* display number of D grades */
printf( "F: %d\n", fCount ); /* display number of F grades */
return 0; /* indicate program ended successfully */
} /* end function main */
if ()
{
func1
}
else if()
{
func2
}
else if()
{
func3
}
else
{
func4
}
//上面这段代码，只可能执行其中某一个func
//下面的代码，则有可能四个func都会执行，或者一个都不执行
if ()
{
func1
}
if()
{
func2
}
if()
{
func3
}
if
{
func4
}
