more arithmetic on non-numbers

* module/language/ecmascript/compile-ghil.scm (comp): Convert to number
  on unary +.

* module/language/ecmascript/impl.scm: Define -, *, /, <, <=, >=, >
  operations on non-numbers.

module/language/ecmascript/compile-ghil.scm

@@ -89,7 +89,8 @@
       (this
        (@impl e l get-this '()))
       ((+ ,a)
-       (make-ghil-inline e l 'add (list (comp a e) (make-ghil-quote e l 0))))
+       (make-ghil-inline e l 'add (list (@impl e l ->number (list (comp a e)))
+                                        (make-ghil-quote e l 0))))
       ((- ,a)
        (make-ghil-inline e l 'sub (list (make-ghil-quote e l 0) (comp a e))))
       ((~ ,a)

module/language/ecmascript/impl.scm

@@ -26,7 +26,7 @@
   #:use-module (language ecmascript array)
   #:re-export (*undefined* *this* call/this*
                pget pput pdel has-property?
-               ->boolean
+               ->boolean ->number
                new-object new new-array)
   #:export (js-init get-this
             typeof
@@ -110,3 +110,32 @@
 
 (define-method (+ a b)
   (+ (->number a) (->number b)))
+
+(define-method (- a b)
+  (- (->number a) (->number b)))
+
+(define-method (* a b)
+  (* (->number a) (->number b)))
+
+(define-method (/ a b)
+  (/ (->number a) (->number b)))
+
+(define-method (< a b)
+  (< (->number a) (->number b)))
+(define-method (< (a <string>) (b <string>))
+  (string< a b))
+
+(define-method (<= a b)
+  (<= (->number a) (->number b)))
+(define-method (<= (a <string>) (b <string>))
+  (string<= a b))
+
+(define-method (>= a b)
+  (>= (->number a) (->number b)))
+(define-method (>= (a <string>) (b <string>))
+  (string>= a b))
+
+(define-method (> a b)
+  (> (->number a) (->number b)))
+(define-method (> (a <string>) (b <string>))
+  (string> a b))