Add operator handling

postfix.s

@@ -39,6 +39,22 @@ wordloop:
 	jmp wordloop
 
 doword:
+	## Skip operator checks if word length is greater than 1
+	cmp $1,%rdx
+	jg donum
+
+	## Check for operators and jump to appropriate procedure
+	movzx (%rsi),%rax
+	cmp $0x2b,%rax
+	je doplus
+	cmp $0x2d,%rax
+	je dominus
+	cmp $0x2a,%rax
+	je domultiply
+	cmp $0x2f,%rax
+	je dodivide
+
+donum:
 	mov $0, %rax
 	mov $0, %rcx
 numloop:
@@ -56,6 +72,38 @@ numloop:
 	jg numloop
 
 	push %rax
+	jmp endword
+
+doplus:
+	pop %rbx
+	pop %rax
+	add %rbx,%rax
+	push %rax
+	jmp endword
+
+dominus:
+	pop %rbx
+	pop %rax
+	sub %rbx,%rax
+	push %rax
+	jmp endword
+
+domultiply:
+	pop %rbx
+	pop %rax
+	imul %rbx,%rax
+	push %rax
+	jmp endword
+
+dodivide:
+	pop %rbx
+	pop %rax
+	mov $0,%rdx
+	idiv %rbx
+	push %rax
+
+	## Restore RDX
+	mov $1,%rdx
 
 endword:
 	## Go back to start if the terminating character (which is in R8)