1 files changed, 15 insertions, 12 deletions

diff --git a/shell/math.c b/shell/math.c
index fa22bc400..077aba848 100644
--- a/shell/math.c
+++ b/shell/math.c
@@ -340,7 +340,20 @@ arith_apply(arith_state_t *math_state, operator op, var_or_num_t *numstack, var_
         if (op == TOK_CONDITIONAL) /* Example: $((a ? b)) */
                 return "malformed ?: operator";
 
-        /* Resolve name to value, if needed */
+        if (PREC(op) < UNARYPREC) {
+                /* In binops a ~ b, variables are resolved left-to-right,
+                 * resolve top_of_stack[-1] _before_ resolving top_of_stack[0]
+                */
+                if (top_of_stack == numstack) /* need two arguments */
+                        goto syntax_err;
+                /* Unless it is =, resolve top_of_stack[-1] name to value */
+                if (op != TOK_ASSIGN) {
+                        err = arith_lookup_val(math_state, top_of_stack - 1);
+                        if (err)
+                                return err;
+                }
+        }
+        /* Resolve top_of_stack[0] name to value */
         err = arith_lookup_val(math_state, top_of_stack);
         if (err)
                 return err;
@@ -360,20 +373,10 @@ arith_apply(arith_state_t *math_state, operator op, var_or_num_t *numstack, var_
                 /* Binary operators */
                 arith_t right_side_val;
 
-                /* Binary operators need two arguments */
-                if (top_of_stack == numstack)
-                        goto syntax_err;
-                /* ...and they pop one */
+                /* Pop numstack */
                 NUMPTR = top_of_stack; /* this decrements NUMPTR */
                 top_of_stack--; /* now points to left side */
 
-                if (op != TOK_ASSIGN) {
-                        /* Resolve left side value (unless the op is '=') */
-                        err = arith_lookup_val(math_state, top_of_stack);
-                        if (err)
-                                return err;
-                }
-
                 right_side_val = rez;
                 rez = top_of_stack->val;
                 if (op == TOK_BOR || op == TOK_OR_ASSIGN)