[英]Top-level expression evaluation at compile time
Is there any way to ensure, that an expression like the following would be evaluated at compile time? 有没有办法确保在编译时评估如下表达式?
myList :: [Int]
myList = sort [3,2,0,1]
If what you're evaluating is an instance of Lift
, you can evaluate it at compile time using TemplateHaskell
: 如果您正在评估的是Lift
的实例,则可以使用TemplateHaskell
在编译时对其进行评估:
{-# LANGUAGE TemplateHaskell #-}
module Sort where
import Data.List
import Language.Haskell.TH.Syntax
myList :: [Int]
myList = $(lift (sort [3,2,0,1] :: [Int]))
If you want, you can check what it has compiled to with -ddump-splices
: 如果需要,可以使用-ddump-splices
检查它编译的内容:
$ ghc -ddump-splices sort
[1 of 1] Compiling Sort ( sort.hs, sort.o )
sort.hs:9:12-41: Splicing expression
lift (sort [3, 2, 0, 1] :: [Int]) ======> [0, 1, 2, 3]
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.