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次の形式のファイルからエスケープされた文字列を読み取るLOLCODEのインタープリターを作成しようとしています。

VISIBLE "HAI \" WORLD!"

次の出力を表示したいと思います。

HAI " WORLD!

これを行うためにprintfのフォーマット文字列を動的に生成しようとしましたが、文字列リテラルの宣言の段階でエスケープが行われているようです。

本質的に、私が探しているのは、この質問の正反対です 。ac文字列の文字をエスケープシーケンスに変換します。

これについて行く方法はありますか？

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It's a pretty standard scanning exercise. Depending on how close you intend to be to the LOLCODE specification (which I can't seem to reach right now, so this is from memory), you've got a few ways to go.

Write a lexer by hand

It's not as hard as it sounds. You just want to analyze your input one character at a time, while maintaining a bit of context information. In your case, the important context consists of two flags:

  • one to remember you're currently lexing a string. It'll be set when reading " and cleared when reading ".
  • one to remember the previous character was an escape. It'll be set when reading \ and cleared when reading the character after that, no matter what it is.

Then the general algorithm looks like: (pseudocode)

loop on: c ← read next character
  if not inString 
    if c is '"' then clear buf; set inString
    else [out of scope here]
  if inEscape then append c to buf; clear inEscape
  if c is '"' then return buf as result; clear inString
  if c is '\' then set inEscape
  else append c to buf

You might want to refine the inEscape case should you want to implement \r, \n and the like.

Use a lexer generator

The traditional tools here are lex and flex.

Get inspiration

You're not the first one to write a LOLCODE interpreter. There's nothing wrong with peeking at how the others did it. For example, here's the string parsing code from lci.

于 2013-09-14T14:23:29.713 に答える