* gash/arithmetic.scm: New file.
* Makefile.am (SOURCES): Add it.
* gash/lexer.scm (get-arithmetic-expansion): New procedure.
(get-expansion): Check for "$((" and use the new procedure to read an
arithmetic expansion.
* gash/eval.scm (word->qword): Handle '<sh-arithmetic>'.
* tests/unit/eval.scm: Add tests.
* tests/spec/Makefile.am (TESTS): Add 'arith'.
* tests/spec/oil.scm: Patch seven of its tests and filter out fifteen
others.
* doc/gash.texi, doc/syntax.txt: Add '<sh-arithmetic>' syntax.
This adjustment paves the way for writing a compiler.
* gash/word.scm (eval-cmd-sub, string-not-null?, word->qword,
expand-word): Move these...
* gash/eval.scm: ...to this module.
* tests/unit/word.scm: Adjust qword tests to use 'expand-qword', and
move non-qword (evaluation) tests to...
* tests/unit/eval.scm: ...this new file, adjusting them to use
'eval-word'.
* Makefile.am (UNIT_TESTS): Add the new file.
Timothy Sample