When lexing a here-end word, expansions should be ignored. That is,
"$x" should be treated as the string "$x" and not a reference to the
parameter named "x".
* geesh/lexer.scm (expansions?): New parameter to enable or disable
treating expansions specially.
(get-double-quotation): Use it.
(get-word): Ditto.
(get-here-end): New public function that reads a token without
treating expansions specially.
* tests/lexer.scm: Test it.
* geesh/lexer.scm (get-quoted-here-doc): New function.
(get-unquoted-here-doc): New function.
(wrap-port-with-tab-trimming): New function.
(get-here-doc): New public function.
* tests/lexer.scm: Test it.
If a dollar sign does not precede a name, it gets treated normally.
* geesh/lexer.scm (get-parameter): Return '#f' if the first character
is not a name character.
(get-parameter-expansion): Propagate the '#f' value.
(get-word): Replace the '#f' value with last character read.
(get-parameter-word): Ditto.
(get-double-quotation): Ditto.
* tests/lexer.scm: Test this.
* geesh/lexer.scm (get-parameter-expression): Use '#f' to signal an
omitted optional word instead of just omitting the word in the
resulting form.
* tests/lexer.scm: Add a test for omitted optional words.
Timothy Sample