Procedure is as follows, to achieve a simple arithmetic, when normal input formula, function normally;
But when a mistake on purpose, such as input///or @ # $, it becomes infinite loop, the scanf don't
Work, a great god answer.

 # include & lt; Stdio. H> 

Int main () 
{
Double d1, d2, d3, 
Unsigned char op, noError=1; 

While (1) 
{
Printf (" please enter a formula, such as 3 + 2: "); 
Lf scanf_s (" % % c % lf ", & amp; D1, & amp; Op, & amp; D2); 

The switch (op) 
{
Case: '+' d3=d1 + d2; break; 
Case '-' : d3=d1, d2, break; 
Case: '*' d3=* d1 d2; break; 
Case '/' : if (d2!=0) 
D3=d1/d2. 
The else 
{
Printf (" divisor cannot be zero!" ); 
NoError=0; 
} 
break; 
Default: printf (" input error, please input again!" ); NoError=0; 
} 
If (noError) 
Printf (" % 5.2 f % c % 5.2 f=% 5.2 f \ n ", d1, op, d2 and d3). 
NoError=1; 
//d1 d2==0; 
//op='+'; 
} 

return 0; 
} 

Intentional mistake style is as follows:

CodePudding user response:

Lf

 scanf_s (" % % c % lf ", & amp; D1, & amp; Op, 1, & amp; D2); 

The lack of a parameter, because % c need to specify the memory size;

Need to pay attention to input format, because the middle is % c, so there can be only one character between d1 and d2, spare one character at a time the results are different, recommended in scanf_s print one day of the following statements to d1, op, compare d2 type and your input

CodePudding user response:

 # include & lt; Stdio. H> 

Int main () {
Double d1, d2, d3, 
Unsigned char op, noError; 

While (1) {
Printf (" please enter a formula, such as 3 + 2 (ctrl-c exit) : "); 
The rewind (stdin); 
Lf the if (3==scanf_s (" % % c % lf ", & amp; D1, & amp; Op, & amp; D2)) {
NoError=1; 
The switch (op) {
Case: '+' d3=d1 + d2; break; 
Case '-' : d3=d1, d2, break; 
Case: '*' d3=* d1 d2; break; 
Case '/' : 
If (d2!=0) {
D3=d1/d2. 
} else {
Printf (" divisor cannot be zero! \n"); 
NoError=0; 
} 
break; 
Default: 
Printf (" input error, please input again! \n"); 
NoError=0; 
} 
If (noError) printf (" % 5.2 lf % c % 5.2 lf=% 5.2 lf \ n ", d1, op, d2 and d3). 
} else {
Printf (" input error, please input again! \n"); 
} 
} 

return 0; 
} 

CodePudding user response:

reference 1/f, confident boy reply:

 scanf_s (lf "% % % c lf", & amp; D1, & amp; Op, 1, & amp; D2); 

The lack of a parameter, because % c need to specify the memory size;

Enter the need to pay attention to the format, because the middle is % c, so there can be only one character between d1 and d2, excess one character at a time the results are different, recommended in scanf_s print one day of the following statements to d1, op, compare d2 type and your input

I don't understand why mistyped, after enters the next cycle, there seems to be no execute the scanf statement, lose the wrong is wrong, this time in the next cycle should be to waiting for input,

CodePudding user response:

refer to the second floor 4 teacher zhao response:

 # include & lt; Stdio. H> 

Int main () {
Double d1, d2, d3, 
Unsigned char op, noError; 

While (1) {
Printf (" please enter a formula, such as 3 + 2 (ctrl-c exit) : "); 
The rewind (stdin); 
Lf the if (3==scanf_s (" % % c % lf ", & amp; D1, & amp; Op, & amp; D2)) {
NoError=1; 
The switch (op) {
Case: '+' d3=d1 + d2; break; 
Case '-' : d3=d1, d2, break; 
Case: '*' d3=* d1 d2; break; 
Case '/' : 
If (d2!=0) {
D3=d1/d2. 
} else {
Printf (" divisor cannot be zero! \n"); 
NoError=0; 
} 
break; 
Default: 
Printf (" input error, please input again! \n"); 
NoError=0; 
} 
If (noError) printf (" % 5.2 lf % c % 5.2 lf=% 5.2 lf \ n ", d1, op, d2 and d3). 
} else {
Printf (" input error, please input again! \n"); 
} 
} 

return 0; 
} 

Look not to understand (# -. -) I am a beginner a I go to the baidu rewind is what

CodePudding user response:

& Op, followed by + 1,

CodePudding user response:

Simply say there is this: the scanf want a fixed format input, but you input errors, so the cycle for the first time, the scanf did not consume the string you entered, then you input error string still exists, and is waiting for consumption, your while loop again, this time, that is, every time you cycle, the scanf in the error string you entered for the answers, but they are not found, so the error string in the input buffer, rewind, probably the input buffer (in fact is the input stream, input buffer is in order to facilitate your understanding, both difference is very big) to empty, so the scanf input cache nothing found, it will wait for your input again