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Fin -- Shorthand functions

The next version of JS is slated to support a shorter syntax for functions that simply return the value of an expression. That's great, but something usable now would be nice. Fin supplies a single function f which can be used to build shorthand functions:

f('$ + $')   // === function(a,b) { return a + b; }
f('$1 + $2') // Same as the previous

Haskell-style "sectioning" is also supported:

f('+1')      // === function(a) { return a + 1; }
f('1+')      // Same
f('+')       // Same as the two functions above
f('.length') // Object attributes are fine
f('.run()')  // as are method calls

Sectioning is only done if an infix operator is found immediately at the beginning/end of the string. Thus, you can inhibit sectioning by preceding/following the string with some whitespace:

f(' -1')     // Constant function, always returns -1

Within this shorthand string, single $ are translated into successive numbered $s. E.g.,

`$ + $ * $` 

is translated into

`$1 + $2 + $3`

Note that this numbering is done ignoring any already-present numbered $s.

$* is translated into a proper array containing the full list of arguments.

$# is translated into an array containing the "rest" of the argument list, after any numbered $ arguments (including implicitly numbered $s).