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Best way to test for a variable's existence in PHP; isset() is clearly broken
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If the variable you are checking would be in the global scope you could do:
array_key_exists('v', $GLOBALS)
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Create or write/append in text file
I have a website that every time a user logs in or logs out I save it to a text file.
7 Answers
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Dynamic Anonymous type in Razor causes RuntimeBinderException
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Anonymous types having internal properties is a poor .NET framework design decision, in my opinion.
Here is a quick and nice extension to fix this problem i.e. by converting the anonymous object into an ExpandoObject right away....
Error installing mysql2: Failed to build gem native extension
I am having some problems when trying to install mysql2 gem for Rails. When I try to install it by running bundle install or gem install mysql2 it gives me the following error:
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Is there an eval() function in Java? [duplicate]
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You can use the ScriptEngine class and evaluate it as a Javascript string.
ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine engine = manager.getEngineByName("js");
Object result = engine.eval("4*5");
T...
Best timestamp format for CSV/Excel?
...to write timestamps that are accurate at least to the second, and preferably to the millisecond. What's the best format for timestamps in a CSV file such that they can be parsed accurately and unambiguously by Excel with minimal user intervention?
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推荐系统算法初探 - 更多技术 - 清泛网 - 专注C/C++及内核技术
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图中，行是不同的用户，列是所有物品，(x, y)的值则是x用户对y物品的评分（喜好程度）。我们可以把每一行视为一个用户对物品偏好的向量，然后计算每两个用户之间的向量距离，这里我们用余弦相似度来算：
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Converting from a string to boolean in Python?
Does anyone know how to do convert from a string to a boolean in Python? I found this link . But it doesn't look like a proper way to do it. I.e. using built-in functionality, etc.
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How to avoid annoying error “declared and not used”
I'm learning Go but I feel it is a bit annoying that when compiling, I should not leave any variable or package unused.
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Mathematical functions in Swift
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As other noted you have several options. If you want only mathematical functions. You can import only Darwin.
import Darwin
If you want mathematical functions and other standard classes and functions. You can import Foundation.
import F...