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honey the codewitch wrote:

3 languages
Regex
C++
C#
To "parse" a fourth, a JSON subset

This brings to mind the children's song about the old lady who swallowed a fly.

The two last verses are:

I know an old lady
Who swallowed a cow.
I don't know how
She swallowed a cow
She swallowed the cow to catch the dog
What a hog to swallow a dog!
She swallowed the dog to catch the cat
Fancy that! To swallow a cat!
She swallowed the cat to catch the bird
How absurd, to swallowed a bird!
She swallowed the bird to catch the spider
That wriggled and tickled inside her.
She swallowed the spider to catch the fly.
I don't know why she swallowed a fly.
Perhaps she'll die...

I know an old lady who swallowed a horse!
She's dead, of course

int16_t dfa_table[] = {
        -1, 1, 6, 1, 34, 34, -1, 1, 12, 1, 117, 117, -1, 1, 18,
        1, 110, 110, -1, 1, 24, 1, 105, 105, -1, 1, 30, 1, 120, 120,
        -1, 1, 36, 1, 116, 116, -1, 1, 42, 1, 105, 105, -1, 1, 48,
        1, 109, 109, -1, 1, 54, 1, 101, 101, -1, 1, 60, 1, 34, 34,
        -1, 1, 66, 1, 58, 58, 0, 0
};

bool match(const int16_t* dfa, int16_t(read_cb)(void*), void* cb_state = nullptr) {
    int tlen;
    int tto;
    int prlen;
    int pmin;
    int pmax;
    int i;
    int j;
    int ch;
    int state = 0;
    bool done;
    bool found = false;
    int acc = -1;
    ch = read_cb(cb_state);
    while (ch != -1) {
        acc = -1;
        done = false;
        while (!done) {
        start_dfa:
            done = true;
            acc = dfa[state++];
            tlen = dfa[state++];
            for (i = 0; i < tlen; ++i) {
                tto = dfa[state++];
                prlen = dfa[state++];
                for (j = 0; j < prlen; ++j) {
                    pmin = dfa[state++];
                    pmax = dfa[state++];
                    if (ch < pmin) break;
                    if (ch <= pmax) {
                        found = true;
                        ch = read_cb(cb_state);
                        state = tto;
                        done = false;

                        goto start_dfa;
                    }
                }
            }
        }
        if (acc != -1) {
            return found;
        }
        ch = read_cb(cb_state);
        state = 0;
    }
    return false;
}