打印F#区分的联合 [英] Printing F# discriminated union

问题描述

我正在编写一个F#程序，该程序将字符串解析为AST类型(区分为联合).

I am writing a F# program which parses a string into a AST type which is a discriminated union.

当我使用fsi(在Mono + Mac OS X上)运行代码时，AST会以一种不错的格式打印出来.但是，当我使用printfn "%s" <| ast.ToString()时，会得到类似FSI_0002.Absyn+clazz的信息.为所有已区分的联合类型编写ToString方法会很麻烦.

When I use fsi (on Mono + Mac OS X) to run my code, the AST is printed out in a nice format. But when I use printfn "%s" <| ast.ToString() I get something like FSI_0002.Absyn+clazz. Writing a ToString method for all the discriminated union types would be a big chore.

如何使值以fsi的方式打印?

How do I make the value print the way fsi does it?

推荐答案

您是否尝试过printfn "%A" ast? %A说明符考虑了 StructuredFormatDisplayAttribute ^[MSDN] (如果存在).

Have you tried printfn "%A" ast? The %A specifier takes into consideration the StructuredFormatDisplayAttribute^[MSDN], if present.

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