From afc9e8f05faddf051aa3a578520d6484ab451282 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@cs.stanford.edu>
Date: Sat, 3 Aug 2019 12:20:08 +0900
Subject: [PATCH] Add + and - operators

---
 main.c  | 22 +++++++++++++++++++++-
 test.sh |  1 +
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/main.c b/main.c
index cae6b4f..7a28076 100644
--- a/main.c
+++ b/main.c
@@ -7,10 +7,30 @@ int main(int argc, char **argv) {
     return 1;
   }
 
+  char *p = argv[1];
+
   printf(".intel_syntax noprefix\n");
   printf(".global main\n");
   printf("main:\n");
-  printf("  mov rax, %d\n", atoi(argv[1]));
+  printf("  mov rax, %ld\n", strtol(p, &p, 10));
+
+  while (*p) {
+    if (*p == '+') {
+      p++;
+      printf("  add rax, %ld\n", strtol(p, &p, 10));
+      continue;
+    }
+
+    if (*p == '-') {
+      p++;
+      printf("  sub rax, %ld\n", strtol(p, &p, 10));
+      continue;
+    }
+
+    fprintf(stderr, "unexpected character: '%c'\n", *p);
+    return 1;
+  }
+
   printf("  ret\n");
   return 0;
 }
diff --git a/test.sh b/test.sh
index eb1e680..ca477d9 100755
--- a/test.sh
+++ b/test.sh
@@ -18,5 +18,6 @@ assert() {
 
 assert 0 0
 assert 42 42
+assert 21 '5+20-4'
 
 echo OK
-- 
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