Add convenience function 'var-ref*'

* geesh/environment.scm (var-ref*): New public function.
* geesh/word.scm (word->qword): Use it to simplify things.

geesh/environment.scm

@@ -23,6 +23,7 @@
             make-environment
             environment?
             var-ref
+            var-ref*
             set-var!
             environment->environ))
 
@@ -50,6 +51,11 @@
 @var{name} is unset, return @code{#f}."
   (assoc-ref (environment-vars env) name))
 
+(define (var-ref* env name)
+  "Get the value of the variable @var{name} in @var{env}.  If
+@var{name} is unset return @code{\"\"}."
+  (or (var-ref env name) ""))
+
 (define (set-var! env name val)
   "Set the variable @var{name} to @var{val} in @var{env}."
   (set-environment-vars! env (acons name val

geesh/word.scm

@@ -112,7 +112,7 @@ and arithmetic substitions using the environment @var{env}."
     (('<sh-cmd-sub> . exps)
      ((eval-cmd-sub) exps))
     (('<sh-ref> name)
-     (or (var-ref env name) ""))
+     (var-ref* env name))
     (('<sh-ref-or> name default)
      (or (var-ref env name)
          (word->qword env (or default ""))))
@@ -150,7 +150,7 @@ and arithmetic substitions using the environment @var{env}."
     (('<sh-ref-skip-min> name pattern) (error "Not implemented"))
     (('<sh-ref-skip-max> name pattern) (error "Not implemented"))
     (('<sh-ref-length> name)
-     (number->string (string-length (or (var-ref env name) ""))))
+     (number->string (string-length (var-ref* env name))))
     (_ (map (cut word->qword env <>) word))))
 
 (define* (expand-word env word #:key (split? #t) (rhs-tildes? #f))