函数外部的变量声明快捷方式

Question

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• Why isn't short variable declaration allowed at package level in Go? 3 answers

Coming from a background in Java and C# I am very pleased with the brevity of Golang's ability to use the shortcut method for variable declaration for private variables within functions, which allows me to write:

x := 1.5

It reminds me of duck typing in a dynamic language such as Python. However, in declaring global variables outside of the scope of a function you still need to use the more verbose syntax of:

var x float64 = 1.5

I'm just wondering why the shortcut method works for private variables and not globals? I know that the designers of the language are quite experienced so I'm assuming that this isn't reflective of a feature overlooked. Is there a technical reason why this kind of type inference (and I realize that the := shortcut is not the same as proper type inference) wouldn't work at the global scope? It just seems somewhat inconsistent in terms of the design, and as an inexperienced Gopher I must admit to being thrown off by this on a couple of occasions. On the whole however I'm really enjoying Go.

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Answer 1

See the Ian's answer in this thread: https://groups.google.com/forum/#!msg/golang-nuts/qTZemuGDV6o/IyCwXPJsUFIJ

At the top level, every declaration begins with a keyword. This simplifies parsing.