inheritance - What does "trait A <: B" mean? -

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स्कला में, 

  विशेषता A & lt ;: B   
 मतलब है? क्या यह केवल 
 
  विशेषता A का विस्तार बी  
 
? 
 
  जोड़ने के लिए संपादित किया गया है:  मैं टाइप मापदंडों के लिए वाक्यविन्यास से परिचित हूं, और उस संदर्भ में  & lt;:  का अर्थ है हालांकि, उपर्युक्त उदाहरण में मुझे यह प्रतीत होता है कि  ए  विशेषता का नाम घोषित किया गया है, एक प्रकार का पैरामीटर नहीं।   
 
 
 एक ही चीज़ को संकलित करने के लिए लगता है।  
  ~ / code / scratch: scala -xprint: typer -e 'trait B; विशेषता ए एंड एलटीः :: 'बी' / 'एसआईपी सार विशेषता बी विस्तारित scala.AnyRef; अमूर्त लक्षण A को java.lang.Object तक फैलाता है। बी ~ / कोड / स्क्रैच: स्कला-एक्सप्रिंट: टाइपर-ए 'गुण बी; विशेषता A का विस्तार बी '/' सीपीयू सार विशेषता बी विस्तारित scala.AnyRef; अमूर्त लक्षण A इस के साथ java.lang.Object को बढ़ाता है। बी  
 
 यह कल्पना "5.3.3 लक्षण" में नहीं समझाता है। लेकिन सिंटेक्स सारांश यह उल्लेख करता है। 
 
  TraitDef :: id = [TypeParamClause] TraitTemplateOpt TraitTemplateOpt :: = TraitTemplate बढ़ाता है | [[Extends] TemplateBody] बढ़ाता है :: = 'विस्तार' | '& Lt ;:'  
 
  UPDATE  इसमें शुरू की गई थी कंपाइलर विकल्प  -Xexperimental  के साथ यह गुण को एक सार के रूप में चिह्नित करता है, प्रस्तावित भाषा सुविधा के साथ उपयोग के लिए।  -Xexperimental  के बिना, यह 'विस्तार' के लिए एक पर्याय है जो केवल लक्षणों के लिए अनुमति है।

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