Add compiler todo note

tools/compiler.c

@@ -4,6 +4,23 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+/*
+
+TODO:
+
+For expressions we should use the shunting yard algorithem.
+This will be useful because it will make it trivial to track types.
+If the type is a literal, we just read it, if it is a variable we read the variable type from the info.
+
+During the first pass we count the number of variables. We assign a local to each variable.
+
+When parsing a expression, we assign any function call or literal to a temp variable slot, 
+(3 maybe?) First one goes in 0, then 2nd in 1, then do operation. Store the operation in 0.
+If it is a function call, use 1 to load and push the args, then use 1 for the return variable.
+If both happen to be function calls use 0, 1, 2. Where 1 & 2 are the function calls, and the result operation gets stored in 0.
+
+*/
+
 #define DEBUG_COMPILER
 
 void emit_byte(u8 byte) {