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printfn“％A”“c”使用F＃

[英]printfn “%A” “c” using F#

原文 2012-03-16 10:10:44 2 2 f#/ string-formatting

By running printfn "%A" "c" , I get "c" . 通过运行printfn "%A" "c" ，我得到"c" 。

By running printfn "%s" "c" , I get c . 通过运行printfn "%s" "c" ，我得到c 。

Why the difference? 为什么不同？ The same goes for char . char 。

2 个解决方案

The %A specifier tries to hint at object types - the "c" is it trying to show it is a string. %A说明符试图暗示对象类型 - "c"是它试图显示它是一个字符串。 When you do %s the compiler knows you want to print a string so it doesn't print the quotes 当您执行%s ，编译器知道您要打印字符串，因此它不会打印引号

Because printfn "%A" uses reflection, it displays results the same as values automatically printed out by F# Interactive. 因为printfn "%A"使用反射，所以它显示的结果与F＃Interactive自动打印的值相同。 On the other hand, %s is for strings only, and it shows contents of strings. 另一方面， %s仅用于字符串，它显示字符串的内容。

The generic case of "%s" is "%O" when ToString methods are used. 当使用ToString方法时， "%s"的一般情况是"%O" 。 The %A specifier is slow, but helpful for structural types and types without overridden ToString methods. %A说明符很慢，但对于没有重写ToString方法的结构类型和类型很有帮助。