1 files changed, 43 insertions, 3 deletions

diff --git a/eval.c b/eval.c
index 5841566..f9f47b6 100644
--- a/eval.c
+++ b/eval.c
@@ -1,14 +1,54 @@
 #include <assert.h>
+#include <inttypes.h>
 #include <stdio.h>
 
 #include "eval.h"
 
-static int evaluate_value(const struct Node* node, long* out)
+static int evaluate_value(const struct Node* node, int64_t* out);
+
+static int complain(const struct Node* node, const char* message)
+{
+    (void)fprintf(stderr, "line %d: %s\n", node->line, message);
+    return 1;
+}
+
+static int evaluate_operands(const struct Node* node, int64_t* left, int64_t* right)
 {
+    if (evaluate_value(node->first, left))
+        return 1;
+
+    return evaluate_value(node->second, right);
+}
+
+static int evaluate_value(const struct Node* node, int64_t* out)
+{
+    int64_t left = 0;
+    int64_t right = 0;
     switch (node->kind)
     {
         case VALUE_DIFFERENCE:
-            *out = (long)node->first->character - (long)node->second->character;
+            *out = (int64_t)node->first->character - (int64_t)node->second->character;
+            return 0;
+        case VALUE_SUM:
+            if (evaluate_operands(node, &left, &right))
+                return 1;
+
+            *out = left + right;
+            return 0;
+        case VALUE_PRODUCT:
+            if (evaluate_operands(node, &left, &right))
+                return 1;
+
+            *out = left * right;
+            return 0;
+        case VALUE_QUOTIENT:
+            if (evaluate_operands(node, &left, &right))
+                return 1;
+
+            if (right == 0)
+                return complain(node, "division by zero");
+
+            *out = left / right;
             return 0;
         default: break;
     }
@@ -42,7 +82,7 @@ static enum RunStatus emit(const struct Node* node)
         return RUN_FAILED;
 
     if (type.kind == KIND_VALUE)
-        (void)printf("%ld\n", type.number);
+        (void)printf("%" PRId64 "\n", type.number);
     return RUN_DONE;
 }