diff --git a/hoax.tal b/hoax.tal
index 5066876..f2c0ef1 100644
--- a/hoax.tal
+++ b/hoax.tal
@@ -50,6 +50,43 @@
 (    40      n/a    rational       rational number (bc/de)           )
 (    50      n/a    bool           (not allocated but used as type)  )
 (    60      n/a    builtin        (not allocated but used as type)  )
+(                                                                    )
+( INVARIANTS                                                         )
+(                                                                    )
+(   1. integers should always be stored in the most compact way      )
+(      a. for integer object n, abs(n) > 16383.                      )
+(   2. long string/symbols have non-empty terminators                )
+(      a. empty strings are only allowed on their own                )
+(      b. empty symbols are never allowed                            )
+(   3. rationals should be in normal form                            )
+(      a. positive denominator > 1                                   )
+(      b. non-zero numerator                                         )
+(      c. gcd(numerator, denominator) should be 1                    )
+(                                                                    )
+( EFFICIENCY                                                         )
+(                                                                    )
+(         EXPRESSION  SIZE (including ref)                           )
+(                 #t   2 bytes                                       )
+(                 #f   2 bytes                                       )
+(                  0   2 bytes                                       )
+(              16383   2 bytes                                       )
+(              16384   7 bytes                                       )
+(              16384   7 bytes                                       )
+(         4294967295   7 bytes                                       )
+(         4294967296  12 bytes                                       )
+(        -4294967295   7 bytes                                       )
+(        -4294967296  12 bytes                                       )
+(    281474976710655  12 bytes                                       )
+(   -281474976710655  12 bytes                                       )
+(               null   2 bytes                                       )
+(         (1 . null)   7 bytes                                       )
+(   (1 . (2 . null))  12 bytes                                       )
+(                 ""   7 bytes                                       )
+(                "a"   7 bytes                                       )
+(             "abcd"   7 bytes                                       )
+(            "abcde"  12 bytes                                       )
+
+( TODO: special case empty string? )
 
 %NL { #0a18 DEO }
 %SP { #2018 DEO }