GADTs使ã£ã¦ã¿ãŸ - Faith and Brave - C++ã§éŠã¼ã†ã“ã®ã‚¨ãƒ³ãƒˆãƒªã¯ã€Haskell Advent Calendar 2011ã®å‚åŠ è¨˜äº‹ã§ã™ã€‚ 今回ã¯ã€Haskellã®GHCæ‹¡å¼µã§ã‚ã‚‹GADTs(Generalized Algebraic Data Types : 一般化代数データ型)を調ã¹ã¦ä½¿ã£ã¦ã¿ãŸã¨ã„ã†å†…容を書ã„ã¦ã¿ã¾ã—ãŸã€‚ 最åˆã«ã€GADTsã¯GHCæ‹¡å¼µãªã®ã§ã€ä½¿ç”¨ã™ã‚‹ã«ã¯ä»¥ä¸‹ã®ã‚ˆã†ã«ã—ã¦æ‹¡å¼µã‚’有効ã«ã™ã‚‹å¿…è¦ãŒã‚ã‚Šã¾ã™ï¼š {-#LANGUAGE GADTs #-} ã¾ãšã¯æ§‹æ–‡çš„ãªé•ã„ã‚’ã€Maybeを例ã«ã—ã¦è¦‹ã¦ã¿ã¾ã—ょã†ã€‚ 通常ã®ä»£æ•°ãƒ‡ãƒ¼ã‚¿åž‹ã§ã¯ã€Maybeã¯ä»¥ä¸‹ã®ã‚ˆã†ã«æ›¸ãã¾ã™ï¼š data Maybe a = Nothing | Just a GADTsã§ã¯ä»¥ä¸‹ã®ã‚ˆã†ã«æ›¸ãã¾ã™ï¼š data Maybe a where Nothing :: Maybe a Just :: a -> Maybe a 通常ã®ä»£æ•°ãƒ‡ãƒ¼ã‚¿åž‹ã§ã¯ã€ãƒ‡ãƒ¼ã‚¿ã‚³ãƒ³ã‚¹
The Mercury Project: Introduction
ã‚ーã„ã€ãƒ†ãƒˆãƒªã‚¹è¨€èªž Tetrlang 完æˆã—ãŸã‚ˆãƒ¼ï¼¼ï¼ˆï¼¾oï¼¾ï¼‰ï¼ - Homoiconic Days
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