at-sign | 易学教程

What does '@' mean in Haskell?

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问题 I've tried googling but come up short. I am furthering my Haskell knowledge by reading some articles and I came across one that uses a syntax I've never seen before. An example would be: reconstruct node@(Node a b c l r) parent@(Node b d le ri) I've never seen these @'s before. I tried searching online for an answer but came up short. Is this simply a way to embed tags to help make things clearer, or do they have an actual impact on the code? 回答1: It is used in pattern matching. Now node

What is the at sign (@) in a batch file and what does it do?

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问题 One remotely familiar with windows/dos batch scripting will recognize this line: @echo off For many-many days, I was happy with the sentiment that the @ is how echo off is meant to be written at the top of the batch and that's it. However, recently I've came accross a line like this: @php foo bar and another line like this: @call \\network\folder\batch.bat This reinforced my suspicion that @ has more to it than just echo mode switching. However @ is not listed in the Windows XP: Command-line

what is the purpose of the @ symbol in front of a variable in octave?

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问题 For example: model = svmTrain(X, y, C, @(x1, x2) gaussianKernel(x1, x2, sigma)); Disclaimer: This is from the Coursera ML class, but it's nearly impossible to search for the @ symbol conventionally. 回答1: @ prefixes the definition of an anonymous function. 回答2: Also, @ is used to demark a function handle. 来源： https://stackoverflow.com/questions/25355028/what-is-the-purpose-of-the-symbol-in-front-of-a-variable-in-octave

What is the at sign (@) in a batch file and what does it do?

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One remotely familiar with windows/dos batch scripting will recognize this line: @echo off For many-many days, I was happy with the sentiment that the @ is how echo off is meant to be written at the top of the batch and that's it. However, recently I've came accross a line like this: @php foo bar and another line like this: @call \\network\folder\batch.bat This reinforced my suspicion that @ has more to it than just echo mode switching. However @ is not listed in the Windows XP: Command-line reference A-Z which I try to use as a reference and thus I'm not sure how to find definitive

Parsing JSON w/ @ at sign symbol in it (arobase)

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My JSON object evaluates to: { "@io": IO, "@type": XXX } If this variable is called my_json , how do I access the @type value of XXX? I tried my_json.@type , but this is giving errors. Help appreciated. Thanks, Nick Use square bracket notation with a string: var XXXValue = my_json['@type']; The same can be used when you have a property name in a variable. Using your same example: var propertyName = '@type'; var XXXValue = my_json[propertyName]; As you've discovered, you can't use an @ symbol in a Javascript variable name, my_json.@type is invalid. The good news for you is that you can access

Parsing JSON w/ @ at sign symbol in it (arobase)

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问题 My JSON object evaluates to: { "@io": IO, "@type": XXX } If this variable is called my_json , how do I access the @type value of XXX? I tried my_json.@type , but this is giving errors. Help appreciated. Thanks, Nick 回答1: Use square bracket notation with a string: var XXXValue = my_json['@type']; The same can be used when you have a property name in a variable. Using your same example: var propertyName = '@type'; var XXXValue = my_json[propertyName]; 回答2: As you've discovered, you can't use an