goto

问题 I have zero experience with writing batch files but my goal does not seem difficult. I'm trying to write a small script that will prompt a user to enter an ID number and then search a directory of .jpgs and copy any pictures containing the ID number to a separate directory. The .jpgs are names xxxxxx_zzz.jpg where xxxxxx is the ID number up to 6 digits and zzz is the sequence number. For example, one ID can have many pictures: 123456_001.jpg, 123456_002.jpg, 123456_003.jpg, etc. I've played

问题 If the statement above is correct, then why when I use reflector on .Net BCL I see it is used a lot? EDIT: let me rephrase: are all the GO-TO's I see in reflector written by humans or compilers? 回答1: The above isn't really correct - it was a polemical device used by Dijkstra at a time when gotos were about the only flow control structure in use. In fact, several people have produced rebuttals, including Knuth's classic "Structured Programming Using Goto" paper (title from memory). And there

问题 What are the performance benefits or penalties of using goto with a modern C++ compiler? I am writing a C++ code generator and use of goto will make it easier to write. No one will touch the resulting C++ files so don't get all "goto is bad" on me . As a benefit, they save the use of temporary variables. I was wondering, from a purely compiler optimization perspective, the result that goto has on the compiler's optimizer? Does it make code faster , slower , or generally no change in

问题 Does the following piece of code constitute undefined behaviour, since I am jumping before the variable declaration and using it via a pointer? If so, are there differences between the standards? int main() { int *p = 0; label1: if (p) { printf("%d\n", *p); return 0; } int i = 999; p = &i; goto label1; return -1; } 回答1: There is no undefined behavior in your program. goto statement has two constraints: (c11, 6.8.6.1p1) "The identifier in a goto statement shall name a label located somewhere

问题 I'm writing a concurrent transaction library in C and found the following problem. Let's consider a sample transaction member pseudo-code, where the "transaction" represents a communication channel with the transaction master: transaction = trans_join(); do_some_ops(); /* receive the data from the master */ trans_rcv(transaction, data); do_some_ops(); trans_send(transaction, answer); /* wait for the possibility for voting */ trans_ready(transaction); /* vote for commiting and wait for the

问题 I am trying to learn C, and I copied a code which calculates VAT> I modified it to recalculate if the user answers yes and exit if the answer in no. To my surprise it behaves in a strange way in that if the answer is yes, it is supposed to go to the beginning as ask the user to enter the item cost. Instead it expects the cost to entered immediately after y is pressed. The code below; /* VAT Calculation*/ #include <stdio.h> #include <stdlib.h> #include <conio.h> #include <string.h> float price

问题 I have a long script calling many other scripts that spit out a lot of figures. For debugging purposes I think it would be useful if -when clicking on a picture- the editor goes to a specific line. Does anyone know if this is possible? I thought I could implement something like A=[]; figure plot(x) A=ginput(1) if A~=[] goto(pointer,line) end The problem is that it only would work only right after that the figure is made. Not at the end of the analysis when I take a look to the figures for

问题 For learning purposes, I wrote the following code snippet: for(int i=0;i<10;i++) { for(int j = 0;j<5;j++) { //(i==j && i==3)? (goto found) : printf("stya here\n"); if(i==j && i==3){goto found;} else {printf("stay here\n");} } } found: printf("yes I am here"); But I wondered when I discovered the omitted statement inside the inner loop not gives error and now I am confused about if-else is not always replaceable with ?: operator. What is the fact here? Why does the commented statement give an

问题 Why do I get the following compiler error: //error CS0159: No such label 'lbl_proc_20' with the following code: //JUST A DUMMY CODE TO ILLUSTRATE THE CONCEPT int a = resultOfFunction1(); int b = resultOfFunction2(); //10+ Local variables that are calculated depending on the results above if (a < 10) { switch (b) { case 0: //Actions for A<10, B=0, using local variables break; case 1: double c = someFunction(a, b); //In real code involves calculations based on a and b if(c > 10.0) goto lbl_proc

问题 The below script will fail with an error, which I'm ok with. Right now, I'm trying to work out my On Error GoTo <label> syntax, and it is currently failing with the following error. Line: 2 Char: 16 Error: Syntax Error Code: 800A03EA Source: Microsoft VBScript compilation error Code below: Sub ComCheck On Error GoTo ErrorHandler Dim fortis Wscript.Echo("Creating COM object.") Set fortis = CreateObject("TESTCOM.APPLICATION") Wscript.Echo("Write Database name.") Wscript.Echo(fortis.Databases[0]