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PASCAL语言子集的词法、语法分析器之实现

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针对简单的文法（PASCAL语言子集），制作相应的词法分析器和递归下降的语法分析器。文法要求如下： 1、关键字、标识符、数字等： 1.begin 2.if 3.then 4.while 5.do 6.end 10.标识符 11.数字 13.+ 14.- 15.* 16./ 17.: 18.:= 20.< 21.<> 22.<= 23.> 24.>= 25.= 26.; 27.( 28.) 2、文法规则: 程序 → begin 语句串 end 语句串 → 语句 { ; 语句 } 语句 → 赋值语句 | 条件语句 | 循环语句赋值语句 → 变量 := 表达式条件语句 → if 条件 then ( 语句 | 程序 ) 循环语句 → while 条件 do ( 语句 | 程序 ) 表达式 → 项 { + 项 | - 项 } 条件 → 表达式关系符表达式关系符 → < | <> | <= | > | >= | = 项 → 因子 { * 因子 | / 因子 } 因子 → 变量 | 数字 | ( 表达式 ) 变量 → 标识符一、词法分析器词法分析器的任务是清除源文件中多余的空格、换行、制表符等，识别文法符号。按顺序输出识别的标识符及其种别编号，供语法分析器调用。代码如下： #include<stdio.h> #include<string.h> #include

How to break Foreach loop in Powershell?

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问题 I'm looking for a way to break my Foreach loop. This is my code $MyArray = @("desktopstudio","controller","storefront","desktopdirector","licenseserver") $component = "toto,blabla" $component = $component.Split(",") foreach ($value in $component) { if ($MyArray -notcontains $value) { Write-host "Your parameter doesn't match" Write-host "Please use one of this parameter $MyArray" Break } } write-host "I'm here" I don't understand why it's not breaking my code, because this is the result when I

How to break Foreach loop in Powershell?

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PHP include/require within a function

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问题 Is it possible to have return statements inside an included file that is inside a function in PHP? I am looking to do this as I have lots of functions in separate files and they all have a large chunk of shared code at the top. As in function sync() { include_once file.php; echo "Test"; } file.php: ... return "Something"; At the moment the return something appears to break out of the include_once and not the sync function, is it possible for the included file's return to break out? Sorry for

After updating to vs2017.3, the breakpoints will not be hit

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问题 We have an asp.net core 2.0 project (migrated from 1.x) running on Vs2017.3 (updated from 2017.2). After the update, breakpoints stop being hit. Vs reports that "The breakpoint will not currently be hit. The source code is different from the original version". Things were normal before updating and migration. The problem can be seen after updating to 2017.3 and before migrating to asp.net core 2.0. I know about the workaround: To right-click and force the breakpoint to be hit even when the

Grails/GSP: break out of <g:each>

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问题 Is there a way to break out of a <g:each>? I have a page wherein I'm iterating through a list and I have to make sure that a checkbox is checked if that was the value stored in DB. To make it a little clearer, please consider something like: <g:each in=${list1}> <g:each in=${list2}> <g:if test="${list1.id == list2.id}"> <input type="checkbox" ... checked="checked" /> </if> </g:each> ... </g:each> where list1 is, say Domain1.list() (i.e. ALL possible values) and list2 is Domain2.find(...) (i.e

c++ continue versus break

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问题 Which statement will be executed after "continue" or "break" ? for(int i = 0; i < count; ++i) { // statement1 for(int j = 0; j < count; ++j) { //statement2 if(someTest) continue; } //statement3 } for(int i = 0; i < count; ++i) { // statement1 for(int j = 0; j < count; ++j) { //statement2 if(someTest) break; } //statement3 } 回答1: continue: ++j and then if j < count then statement2 otherwise statement3 break: statement3 回答2: Continue jumps straight to the top of the innermost loop, where the

c++ continue versus break

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Why can't I use break in a C# ternary expression?

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问题 I am trying to convert the if else clause to a ternary within a while loop, however it's not allowing me to have a break after the question mark, pointing an error at the break as an invalid expression. How would I go about turning this simple if else into a ternary like so. while (true) { Console.WriteLine("Enter 3 words seperated by spaces: "); var input = Console.ReadLine(); //input == "" ? break : ConvertToPascal(input); if (input == "") break; else ConvertToPascal(input); } } 回答1: It isn

Break outside loop Python function other options

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问题 I have some code: def playAgain1(): print("Would you like to keep boxing or quit while you are ahead? (y/n)") playAgain = input().lower() if(playAgain.startswith('y') == False): print("Whatever you chicken.") break I want it to break the loop if playAgain() doesn't start with y . Whenever I try, I get the error: 'break' outside loop How could I write this better to make it work? 回答1: As Matt Bryant's answer states, you can't break outside a loop but can just return from the function. I would