PhraseCache is a simple language for matching user input.

  (see also https://PhraseCache.best)

A PhraseCache expression can consist of:

  ** just a WORD OR PHRASE, e.g.:

     school

     lunch time

   This will match when the phrase appears anywhere in the input, e.g.:

     Is it lunch time now?

  ** a QUOTED STRING, e.g.:

     "q&a"

     "\o/"

   These strings can contain any special character. They are

   matched exactly character-by-character, but are

   case-insensitive. The pattern does not match when it's part

   of a bigger word (e.g. the first example would not match

   the input "faq&answers").

   So the second line will match e.g. these inputs:

     That's cool \o/

     \O/

   You can even match quotes, like this:

     "\"hello\""

   This will only match a "hello" actually put in quotes by

   the user.

  ** "OR" combination (comma)

     fun, enjoying

   matches when any of the elements is present in input.

   So the example matches "this is fun" as well as

   "I am enjoying this".

  ** "AND" combination (plus)

     this + that

   requires all elements to be present in input (in any order).

   So the example matches "this and that" and "that or this",

   but not "this one" or "that one".

   "and" takes precedence over "or", so:

     the + solution, a + resolution

   is the same as:

     (the + solution), (a + resolution)

   (See "bracketing" below.)

  ** NEGATION (exclamation mark in front)

     great + !not

   matches "this is great", but not "this is not that great".

  ** match START OF LINE only (with ^)

     ^hello bot

   will match "hello bot friend", but not "oh hello bot".

  ** match END OF LINE only (with $)

     please do this$

   will match "now please do this", but not "please do this now".

   Start of line and end of line can be combined like this:

     ^ok!$

   matches just "ok" and nothing else. (See "typo" section

   below.)

  -BRACKETING (grouping)

     (quick, fast) + (solution, resolution)

   will match "we need a fast solution" as well as "the

   resolution should be quick".

  ** DISALLOW TYPOS with exclamation mark, e.g.:

     hi!

   By default, PhraseCache has a crude typo detection system

   that allows one typo (1 character added, removed or inserted

   per input row). It's a cool feature, but arguably could see

   some improvement. For naive patterns, it sometimes fails

   badly, e.g. input "I" will also match the pattern "hi".

   To circumvent this, add an exclamation mark AFTER the phrase

   in question. (Not before the phrase as that would mean

   negation.)

Advanced features (not really used currently):

  -add a weight to a sub-pattern:

    (foo, bar)*0.5