syntax

问题 When the PSDrive is not specified, the following works: ${[foo]}="bar" echo ${[foo]} But the following does not work $env:${[foo]}="bar" At line:1 char:1 + $env:${[foo]}="bar" + ~~~~~ Variable reference is not valid. ':' was not followed by a valid variable name character. Consider using ${} to delimit the name. At line:1 char:6 + $env:${[foo]}="bar" + ~~~~~~~~~~~~~~ Unexpected token '${[foo]}="bar"' in expression or statement. + CategoryInfo : ParserError: (:) [],

问题 I've seen a few other questions and answers stating that let _ = foo() destroys the result at the end of the statement rather than at scope exit, which is what let _a = foo() does. I am unable to find any official description of this, nor any rationale for this syntax. I'm interested in a few inter-twined things: Is there even a mention of it in the official documentation? What is the history behind this choice? Is it simply natural fall-out from Rust's binding / destructuring rules? Is it

问题 I've seen a few other questions and answers stating that let _ = foo() destroys the result at the end of the statement rather than at scope exit, which is what let _a = foo() does. I am unable to find any official description of this, nor any rationale for this syntax. I'm interested in a few inter-twined things: Is there even a mention of it in the official documentation? What is the history behind this choice? Is it simply natural fall-out from Rust's binding / destructuring rules? Is it

问题 I have recently seen blocks of C++ code where there is a "\" after each semicolon. It seems very odd to me. Perhaps it is nothing more than a mistake or the remnants of some long forgotten comments (although those have a forward slash "/" ). What impact would this "\" have on the code? Her is a code sample. #define PE_DECLARE_CLASS(class_) \ typedef class_ MyClass; \ static void setSuperClasses(); \ 回答1: A backslash as last character in a line causes this line to be joined with the next for

问题 I want code that can analyze a function call like this: whatever(foo, baz(), 'puppet', 24+2, meow=3, *meowargs, **meowargs) And return the positions of each and every argument, in this case foo , baz() , 'puppet' , 24+2 , meow=3 , *meowargs , **meowargs . I tried using the _ast module, and it seems to be just the thing for the job, but unfortunately there were problems. For example, in an argument like baz() which is a function call itself, I couldn't find a simple way to get its length. (And

问题 What are the benefits of using with() ? In the help file it mentions it evaluates the expression in an environment it creates from the data. What are the benefits of this? Is it faster to create an environment and evaluate it in there as opposed to just evaluating it in the global environment? Or is there something else I'm missing? 回答1: with is a wrapper for functions with no data argument There are many functions that work on data frames and take a data argument so that you don't need to

问题 Quick question; I've recently upgraded to VS2010, and got the new version of ReSharper. Now, when ReSharper is giving me autocomplete options for a variable, it give me the option of < variableName >: What does the : stand for? For example; I have this: var productIds = new List<int>(inventoryItemsToProcess.Keys); And when I start typing out a line like this: var lastOrderDates = GetProductLastOrderDates(pro It gives me the option for productIds as well as productIds: What's the difference

问题 I was hoping to get some clarity on the use of () before the call of a method (applies to class,struc, etc as well). Firstly I don't know what the action is called so having trouble in pinpointing where to start reading on it, and secondly if you have some explanation on why one would use this that would be great. In the example below I am interested in the (TestClassRemoting) that is called in front of the Activator.Getobject(...) method. Example TestClassRemoting test = (TestClassRemoting

问题 I get a console error: 'Uncaught SyntaxError: Unexpected token -' What's wrong? Please, may anyone help? $(document).ready(function() { $("#widget_settings_holder").find(".tbLanguageTabs").first().tabs(); var cmpt-br = CodeMirror.fromTextArea(document.getElementById("text_widget_text_pt-br"), { mode: "htmlmixed", lineNumbers: true, tabMode: "indent" }); $(tbApp).off("tbWidget:onUpdate.textWidget").one("tbWidget:onUpdate.textWidget", function(event, $widget, $form) { if ($widget.attr("id")

问题 I just got started looking at using Solr as my search web service. I don't know whether Solr supports these query types: Startswith Exact Match Contain Doesn't Contain In the range Could anyone guide me how to implement those features in Solr? Cheers, Samnang 回答1: Solr is capable of all those things but to adequately explain how to do each of time an answer would become a mini-manual for Solr. I'd suggest you read the actual manual and tutorials linked from the Solr homepage. In short though: