使用 parsec 在字符串中查找子字符串

Question

例如，我想从 "aabbccabc" 得到 "abc"，使用正则表达式应该很容易。但我想使用秒差距。好像try可以做到，但那肯定效率很低...

我试过了：

import Text.ParserCombinators.Parsec
ps pser txt = case (parse pser  "" txt ) of
  Left e  -> show e
  Right v -> v

得到以下结果：

λ> ps (string "asf") "  dsfdsasf"
"(line 1, column 1):\nunexpected \" \"\nexpecting \"asf\""

Answer 1

你可以这样做：

{-# LANGUAGE FlexibleContexts #-}

import Text.Parsec
import Text.Parsec.Char

findSubString str = try (string str) <|> (anyChar *> findSubString str)

foo = do
  findSubString "abc"
  findSubString "def"

test1 = parseTest foo "this is abc"         -- fails: expecting def

test2 = parseTest foo "this is abc and de"  -- fails: expecting def

test3 = parseTest foo "this is abc and def" -- succeeds

使用 parsec 在字符串中查找子字符串

Find substring in a string with parsec

haskell

parsec