undefined

问题 Is it possible to treat warnings as errors in a Makfile (and thus exit before Makefile proceeds) Furthermore, is it possible to filter out which warning yields an error? My use case: I want to use --warn-undefined-variables in combination with this so that Makefile will exit when a variable is undefined, which is a very common source of error. Obviously I don't want to manually check for each variable as this is error-prone/tedious. I couldn't find anything on this, but it's a pretty

问题 When writing a script that loads data, it's a waste of time to wait for it to load each time. How to check to see if the variable is defined? 回答1: You can use the exist function in Octave to do the work. It can be used to check the existence of given name as a variable, built in function, file, or directory. In you case, to check the existence of a variable, you may use something like this: if (exist("your_var_name", "var") == 1) printf("varname exists"); else printf("varname not exists");

问题 I'm a bit confused about how best to check if a variable is undefined or not in javascript. I've been doing it like this: myVar === undefined; But is it better in all cases to use typeof instead? typeof myVar === undefined; And what about the use of undefined vs "undefined" , which I've also seen? 回答1: This is the best way to check -- totally foolproof: typeof myVar === "undefined" This is OK, but it could fail if someone unhelpfully overwrote the global undefined value: myVar === undefined;

问题 Trying to populate a Collection from a list of values, I am getting an error about the Collection's model 's prototype being undefined. Looking at this question about a similar problem, I have checked that the Model is actually created before the collection is instanced, to the best of my ability. The error is being thrown in one of the event handlers of the Marionette CompositeView that holds the Collection, after fetching the data from the server and trying to reset the collection with the

问题 I have the below class (which is basically a wrapper for std::vector), and one of the functions returns a variable of the type AInteger (which is basically a wrapper for int). Now the type AInteger is used multiple times throughout the class, yet the compiler starts complaining at a very specific position. When I remove the "getSize()" function, everything compiles just fine. There is mutual inclusion, so I need the forward declaration for everything to work. One of the problems is that the

问题 I am totally new to Android. This question might be a basic one. But I'm struggling for four days with this. Please Help me. I'm making horizontal listview for providing the contents of several categories from blog. (similar interface with Pulse news app) I got the open source of the horizontal listview and I'm modifying it. This code is CustomArrayAdapter.java . But when I try to write super() ; inside the constructor, it makes an error like this : The constructor ArrayAdapter<ArrayList

问题 I've written some code that finds overlapping keys in 3 different HoAs that contain some information on which I sort them later: #!/usr/bin/perl use warnings; use strict; my @intersect; for my $key (sort keys %hash1) { if (exists $hash2{$key} && $hash3{$key} ) { my ($hit1, $percent_id1) = @{ $hash1{$key}[-1] }; my ($hit2, $percent_id2) = @{ $hash2{$key}[-1] }; my ($hit3, $percent_id3) = @{ $hash3{$key}[-1] }; push @intersect, "$key\tC1:[$condition1]$hit1 [$percent_id1]\tC2:[$condition2]$hit2

问题 Can anything be done to define a Show instance for an undefined value? Maybe some GHC extensions exist? I want something like this: > print (1,undefined) (1,"undefined") 回答1: According to the Haskell 2010 report, chapter 9, evaluating undefined should always cause an error: -- It is expected that compilers will recognize this and insert error -- messages that are more appropriate to the context in which undefined -- appears. undefined :: a undefined = error "Prelude.undefined" Since printing

问题 This question already has answers here : “Undefined function 'function_name' for input arguments of type 'double'.” (3 answers) Closed 3 years ago . I'm trying to write a function that does what conv2(h1,h2,A) & conv2(...'shape') does without using the built-in function. (speed is currently not an issue). as defined here: http://www.mathworks.co.uk/help/matlab/ref/conv2.html These are my commands: imgC = imread('camerman.tif'); imgC = double(imgC); sigma = 1; inp = (-1 .*2.5 .*sigma):1:(2.5 .

问题 I am trying to redirect to an URL if the Facebook Like button has been pressed, but it doesn't work, and results having an error in the source view saying "FB is not defined" Here's my redirect code: FB.Event.subscribe('edge.create', function(response) { location.href = 'censored'; } ); and here's the FB like button <div id="fb-root"></div> <script>(function(d, s, id) { var js, fjs = d.getElementsByTagName(s)[0]; if (d.getElementById(id)) return; js = d.createElement(s); js.id = id; js.src =