while-loop

问题 I have the following for loop, I am prompting the user to enter a 4 digit pin and hit enter. Can someone explain to me what the while loop is really doing because I don't fully understand it. //user input for pin for(i = 0; i < PIN_LENGTH; i++) { printf("Enter digit %d of your PIN: ", i); user_pin[i] = getchar(); while (getchar() != '\n'); //what is this line doing?? } 回答1: When you give input to the program, then you end it with the Enter key. This key is sent to your program as a newline.

问题 We have have a certain amount e.g. 300 units. This amount should be as evenly as possible distributed over 40 "slots" or "bins". It would be easy if each slot would be the same - so it would be 7,5 at each slot. However, the slots vary in size and we cannot "fill in" there more than its "size" allows for e.g. if its only 4. What we cannot "fill in" more than 4. Hence, we have to distribute more over the other ones. Lets assume that there is another limitation: A general filling in limit of e

问题 The eventual goal is to have my bash script execute a command on multiple servers. I almost have it set up. My SSH authentication is working, but this simple while loop is killing me. When I execute the while loop, reading my file for host names, it works fine when I run a ssh $HOST "uname -a" but when I attempt to run another ssh command, ssh $HOST "oslevel -s" the while loop ends early! I can't figure it out. Why would the while read do loop run perfectly fine with the first command, but

问题 From this answer: Is there a way to loop through a table variable in TSQL without using a cursor? I'm using the method WHILE EXISTS(SELECT * FROM #Temp) The problem is that it's outputting multiple tables, if possible I'd like to output as a single table. Declare @Id int WHILE EXISTS(SELECT * FROM #Temp) Begin Select Top 1 @Id = Id From #Temp --Do some processing here Delete #Temp Where Id = @Id End So right now it outputs this: x y -- -- 1 a x y -- -- 1 b But I'd like it to output this: x y

问题 I usually loop through lines in a file using the following code: open my $fh, '<', $file or die "Could not open file $file for reading: $!\n"; while ( my $line = <$fh> ) { ... } However, in answering another question, Evan Carroll edited my answer, changing my while statement to: while ( defined( my $line = <$fh> ) ) { ... } His rationale was that if you have a line that's 0 (it'd have to be the last line, else it would have a carriage return) then your while would exit prematurely if you

问题 I've seen two ways to create an infinite loop in Python: while 1: do_something() while True: do_something() Is there any difference between these? Is one more pythonic than the other? 回答1: Fundamentally it doesn't matter, such minutiae doesn't really affect whether something is 'pythonic' or not. If you're interested in trivia however, there are some differences. The builtin boolean type didn't exist till Python 2.3 so code that was intended to run on ancient versions tends to use the while 1

问题 Can we put semicolon like while(condition); in a C Programming? If while(condition); is valid, what does it mean? 回答1: while (condition); is the same as while (condition) { } It can be used for waiting loops, e.g.: while (!isLightGreen()); // waits until isLightGreen() returns true go(); 回答2: It means the body of the loop is empty. Typically this pattern is used when the condition itself does some work. For example, this loop can copy bytes within the condition: while ( '\0' != (*pt++ = *ps++

问题 I cannot figure out why program control does not reach the third printf, right after the for loop. Why won't the third printf print? If I change the for loop to while loop, it still will not print. Here is the program and output: main() { double nc; printf ("Why does this work, nc = %f\n", nc); for (nc = 0; getchar() != EOF; ++nc) { printf ("%.0f\n", nc); } printf ("Why does this work, nc = %f", nc); } The output is: Why does this work, nc = 0.000000 test 0 1 2 3 4 回答1: It works fine for me,

问题 As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 7 years ago . When I was taking CS in college (mid 80's), one of the ideas that was constantly repeated was to always write loops which test at the

问题 I am running a loop through a folder in order to get the complete filename address (folders address + file name and extension). I am using the following, but at some point the Dir value is <Invalid procedure call or argument> recsFolder = Functions.GetFolder("C:\") recfile = recsFolder & "\" & Dir(recsFolder & "\*.rec*") Do While Len(recfile) > 0 recfile = recsFolder & "\" & Dir Loop The error is thrown before the loop as completed reading all the files. EDIT: another approach and Dir is