Updated documents for removal of Boolean.

Clarified semantics for expressions regarding boolean.

doc/Literals.md

@@ -16,6 +16,11 @@ This page explains literals.
 
     boolean: 'true' | 'false' ;
 
+xemmai has no boolean type.
+The only falsy value is `null`. The other values are all truthy.
+`true` is an alias for `1.0`, which is float not integer `1` because bitwise operators have to distinguish integer operations and boolean operations.
+`false` is an alias for `null`.
+
 ## Integer Literals
 
     integer: digit+ ;

doc/ObjectTraits.md

@@ -66,7 +66,6 @@ It can be called only if the object is in the shared state which means no thread
     Method      no         *1
     Throwable   yes        *3
     Null        no         *1
-    Boolean     no         *1
     Integer     yes        *4
     Float       yes        *4
     String      no         *1

doc/StackUsage.md

@@ -104,9 +104,6 @@
     NUL
         |
         |N
-    BOOLEAN
-        |
-        |B
     INTEGER
         |
         |I

doc/TermExpressions.md

@@ -10,6 +10,8 @@ See [PrimaryExpressions](PrimaryExpressions.md).
 
     unary: ('+' | '-' | '!' | '~')* primary ;
 
+Negate operator (`!`) returns `true` (`1.0`) if the operand is `false` (`null`), returns `false` (`null`) otherwise.
+
 ## Multiplicative Expressions
 
     multiplicative: unary (('*' | '/' | '%') unary)* ;
@@ -26,13 +28,21 @@ See [PrimaryExpressions](PrimaryExpressions.md).
 
     relational: shift (('<' | '>' | '<=' | '>=') shift)* ;
 
+Relational, equality, and identity operators return either `true` (`1.0`) or `false` (`null`).
+
 ## Equality Expressions
 
     equality: relational (('==' | '!=') relational)* ;
 
+## Identity Expressions
+
+    identity: equality (('===' | '!==') equality)* ;
+
 ## And Expressions
 
-    and: equality ('&' equality)* ;
+    and: identity ('&' identity)* ;
+
+Bitwise operators (`&`, `^`, and `|`) do bitwise operations if both the operands are integers, do boolean operations if neither are integers, throws an exception otherwise.
 
 ## Xor Expressions
 
@@ -46,10 +56,14 @@ See [PrimaryExpressions](PrimaryExpressions.md).
 
     and_also: or ('&&' or)* ;
 
+Evaluates the left operand, returns it if it is `false` (`null`), evaluates the right operand and returns it otherwise.
+
 ## Or Else Expressions
 
     or_else: and_also ('||' and_also)* ;
 
+Evaluates the left operand, returns it if it is not `false` (`null`), evaluates the right operand and returns it otherwise.
+
 ## Conditional Expressions
 
     conditional: or_else ('?' conditional ':' conditional)? ;

doc/WalkThrough.md

@@ -12,8 +12,8 @@ This document walks through xemmai language.
     1.5 * 2.0 # => 3.0
     "This is a string."
     null
-    true
-    false
+    true # => 1.0
+    false # => null
 
 ## Variables