- scsh integration
  Affected: fr nawk filemtch glob rdelim re scsh-interfaces scsh-package

- Naming conventions. "re" vs. "regexp", should I have "smart" versions
  of make-re-string, etc.

- Remove all "reduce" forms from scsh, replace with foldl, foldr forms.
  - Check FPS, network code

- The match fun should allow you to state the beginning of string is not a
  real bos & likewise for eos. Similarly for bol & eol.
  execution flag: 
    -- REG_NOTBOL -- beginning of string doesn't count as ^ match.
    -- REG_NOTEOL -- end       of string doesn't count as $ match.

- Hack awk, expect, chat, dir-match for new regexp system
  Current:
  (awk (test body ...)
       (:range test1 test2 body ...)
       (else body ...)
       (test => proc)
       (test ==> vars body ...))

  test ::=
    integer
    expression
    string


  New:
  (else body ...)
  (:range test1 test2 body ...)
  (after body ...)
  (test => proc)
  (test ==> vars body ...)
  (test body ...)

  test ::= integer | sre | (WHEN exp) | exp

-------------------------------------------------------------------------------
Must disallow, due to Posix' RE_CONTEXT_INVALID_OPS
    ...^*...
    *... ...(*... ...|*...
    |... ...| ...|$... ...||... ...(|...

    That is: 
    1. Do simplification below to remove repeats of zero-length matches.
    2. An empty elt of a choice renders as ().
    3. ...|$... Hack it: If first char of a rendered choice elt is $, prefix
       with ().

    Simplify ^{0,n} -> ""
             ^{m,n} -> ^     (0<m<=n)
             ^{m,n} -> (in)  (m>n)
	     Similarly for bos/eos bol/eol bow/eow ""

    Spencer says:
       A repetition operator (?, *, +, or bounds)  cannot  follow
       another repetition operator.  A repetition operator cannot
       begin an expression or subexpression or follow `^' or `|'.

       `|'  cannot  appear  first or last in a (sub)expression or
       after another `|', i.e. an operand of  `|'  cannot  be  an
       empty  subexpression.   An  empty parenthesized subexpres-
       sion, `()', is legal and matches an empty (sub)string.  An
       empty string is not a legal RE.


Fix the printer and reader so control chars are printed as
    \ddd; do syntax for control-char input

-------------------------------------------------------------------------------
Less important:
- Support for searching vs. matching
- Case-scope hacking (needs s48 0.51 CODE-QUOTE)
- simp caching
- Better char-set->sre renderer
  First, bound the cset with tightest possible superset,
  then look for negations.

Possible interesting extensions:
- An ADT->DFA compiler
- A DFA->Scheme-code compiler
- An ADT interpreter
- A pattern notation for matching against s-expressions.
  This would be handy for specifying the grammar of Scheme macros,
  for example.
- Only allocate svec and evec if we match?
