Update Documentations for Cast and TypesTable

docs/expression/case.md

@@ -1,3 +1,5 @@
+### Case expression
+
 Case expression is similar to Switch Expression in many languages, it's return the value of the first branch that has condition evaluated to true, if not branch found it will return the default value
 
 ```sql

docs/expression/cast.md

@@ -0,0 +1,29 @@
+### Cast expression
+
+In GitQL there are two types of casting, Explicit and Implicit casting
+
+#### Implicit Casting
+
+Implicit casting is performed without the need from you to write cast operator or function for example
+
+```sql
+SELECT True = 't'
+```
+
+In this case the engine perform implicit cast from Text 't' to become boolean 'true' so it's end up with
+
+```sql
+SELECT True = True
+```
+
+The same is performed when you write Date, Time or DateTime as String and pass it to function that accept Date.
+
+#### Explicit Casting
+
+Implicit casting can handle some cases when the value is const and has specific pattern, but in some cases you want for example
+to cast Float to Int or Int to Float after the value is evaluated or provided from real data, in this case you need to explicit ask the engine
+to case this value to another type, for example
+
+```SQL
+SELECT CAST(commits_count AS Real);
+```

docs/expression/index.md

@@ -3,5 +3,6 @@ GitQL Expressions
 - [Binary expressions](binary.md).
 - [Unary expressions](unary.md).
 - [Case expression](case.md).
+- [Cast expression](cast.md)
 - [Array expression](array.md).
 - [Access Member](access.md).

docs/sdk/types.md

@@ -65,4 +65,22 @@ impl DataType for IntPairType {
 }
 ```
 
-Now if we create a new Function with Signature that accept IntPair and we pass Int, it will report an error, but now we created a Type but to create a Value with this type we need to create a Custom Value too ([Creating the IntPairValue as Custom value](values.md)).
+Now if we create a new Function with Signature that accept IntPair and we pass Int, it will report an error, but now we created a Type but to create a Value with this type we need to create a Custom Value too ([Creating the IntPairValue as Custom value](values.md)).
+
+### Register your type in TypesTable
+
+If you want to support using your type in explicit casting feature, for example
+
+```SQL
+SELECT CAST(value AS IntPairType)
+```
+
+You must register your type to the TypesTable component and pass it to the `Environment` for example
+
+```rust
+let types_table = TypesTable::new();
+types_table.register("intpair", Box::new(IntPairType));
+
+let env = Environment::new();
+env.register_types_table(types_table);
+```

mkdocs.yml

@@ -104,6 +104,7 @@ nav:
       - Unary: expression/unary.md
       - Binary: expression/binary.md
       - Case: expression/case.md
+      - Cast: expression/cast.md
       - Access Member: expression/access.md
     - STD Functions and Operators:
       - "functions/index.md"