如何在haskell中获取变量名称 [英] How to get variable name in haskell

问题描述

#define print（a）printf （％s =％d \\\
，#a，a）

int a = 5;
print（a）;

应该列印

  a = 5 
  

？

  { - ＃LANGUAGE TemplateHaskell 
 
 ＃ - } 
 module Pr其中
 import Language.Haskell.TH 
 import Language.Haskell.TH.Syntax 
 
 pr ::名称 - > ExpQ 
 pr n = [| putStrLn（$（lift（nameBase n ++=））++ show $（varE n））|] 
  

然后在另一个模块中：

  { - ＃LANGUAGE TemplateHaskell＃ - } 
 import Pr 
a =hello
 main = $（pr'a）
  

I came to haskell having some c background knowledge and wondering is there an analog to

#define print( a ) printf( "%s = %d\n", #a, a )

int a = 5;
print( a );

that should print

a = 5

?

解决方案

Here's the TH solution augustss mentioned:

{-# LANGUAGE TemplateHaskell #-}
module Pr where
import Language.Haskell.TH
import Language.Haskell.TH.Syntax

pr :: Name -> ExpQ
pr n = [| putStrLn ( $(lift (nameBase n ++ " = ")) ++ show $(varE n) ) |]

then in another module:

{-# LANGUAGE TemplateHaskell #-}
import Pr
a = "hello"
main = $(pr 'a)

这篇关于如何在haskell中获取变量名称的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！