CODEWITHSUNDEEP
c++stringescaping
paul23
paul23

Reputation: 9435

parsing user string, escape characters

How can I parse a string and replace all occurences of a \. with something? Yet at the same time replace all \\ with \ (literal).. Examples:

hello \. world => hello "." world
hello \\. world=> hello \. world
hello \\\. world => hello \"." world

The first reaction was to use std::replace_if, as in the following:

    bool escape(false);
    std::replace_if(str.begin(), str.end(), [&] (char c) {
        if (c == '\\') {
            escape = !escape;
        } else if (escape && c == '.') {
            return true;
        }
        return false;
    },"\".\"");

However that simply changes \. by \"." sequences. Also it won't be working for \\ parts in the staring.

Is there an elegant approach to this? Before I start doing a hack job with a for loop & rebuilding the string?

Upvotes: 1

Views: 1797

Answers (1)

Léo
Léo

Reputation: 88

Elegant approach: a finite state machine with three states:

  • looking for '\' (iterating through string)
  • found '\' and next character is '.'
  • found '\' and next character is '\'

To implement you could use the iterators in the default string library and the replace method.

http://www.cplusplus.com/reference/string/string/replace/

Upvotes: 2

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