arithmetic: Port to Mes.

* gash/arithmetic.scm (define-module): Import SRFI 14.
* gash/eval.scm (eval-arithmetic): New procedure.
(word->qword): Use it to abstract away the differences in 'eval'
between Guile and Mes.

gash/arithmetic.scm

@@ -21,6 +21,7 @@
   #:use-module (ice-9 match)
   #:use-module (ice-9 receive)
   #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-14)
   #:use-module (srfi srfi-26)
   #:use-module (system base lalr)
   #:export (read-arithmetic))

gash/eval.scm

@@ -36,6 +36,17 @@
 ;;;
 ;;; Code:
 
+(cond-expand
+ (mes
+  (define (eval-arithmetic expr)
+    (eval `(begin (number->string ,expr))
+          (current-environment))))
+ (else
+  (define (eval-arithmetic expr)
+    (eval `(begin (use-modules (gash environment))
+                  (number->string ,expr))
+          (interaction-environment)))))
+
 (define eval-cmd-sub
   (make-parameter (lambda (exps) (throw 'eval-cmd-sub-unset))))
 
@@ -55,9 +66,8 @@ and arithmetic substitions."
      ((eval-cmd-sub) exps))
     (('<sh-arithmetic> word)
      (let* ((arithmetic (expand-word word #:output 'string))
-            (expr `(begin (use-modules (gash environment))
-                          (number->string ,(read-arithmetic arithmetic)))))
-       (eval expr (interaction-environment))))
+            (expr (read-arithmetic arithmetic)))
+       (eval-arithmetic expr)))
     (('<sh-ref> name)
      (parameter-ref name ""))
     (('<sh-ref-or> name default)