upd readme - syntax etc

docs/readme.md

@@ -52,8 +52,168 @@ File extension - `*.de` (because `de` is more short than `def`).
 
 
 # 2. Syntax and Ideas
-todo
 
 
+## 2.1 toml file for config keys-values
+
+```toml
+[lexer]
+indent_type = 0
+indent_matter = 4
+indent_not_matter = 2
+```
+this means we have basic indent (Off-side rule) as 4 whitespaces,  
+but we do not got error when next line have 5, 6 or 3, 2 whitespaces -  
+needs to have more that 2 whitespaces for change indent (Off-side rule) for next level.
+
+
+## 2.2 do not use any reserved words (keywords) for function definition (like in Erlang)
+todo add examples
+
+
+## 2.3 Pattern Matching that transforms into ```if .. else if .. else ..```
+todo think - there are ```case``` in dlang already (maybe use ```case .. of``` ?):  
+https://dlang.org/spec/statement.html#SwitchStatement  
+https://dlang.org/spec/statement.html#case-range  
+https://tour.dlang.org/tour/uk/basics/controlling-flow  
+https://dlang.org/spec/expression.html#IsExpression  
+todo add examples
+
+
+## 2.4 Pattern Matching at functions too (like in Erlang)
+Function overloading in dlang allows to define the same function but with different versions for different data types:
+```dlang
+int my_func(int x) {
+    return x;
+}
+
+int my_func(string x) {
+    return x.length; // or other operation(s) with argument
+}
+```
+that similar to erlang's functions clauses:
+```erlang
+my_func(X) when is_integer(X) -> X;
+my_func(Y) when is_binary(Y) orelse is_list(Y) -> string:length(Y). %% is_list for list string (list chars codes)
+```
+
+other example
+```erlang
+my_func(1) -> 1;
+my_func(5) -> 5 * 2;
+my_func(9) -> 9 * 3;
+my_func(X) -> X * 4.
+```
+->
+```dlang
+int my_func(int x) {
+    if (x == 1) return 1;
+    else if (x == 5) return x * 2;
+    else if (x == 9) return x * 3;
+    else return x * 4; // other cases
+}
+
+// or
+
+int my_func(int x) {
+    switch (x) {
+        case 1:
+            return 1; // if x == 1
+        case 5:
+            return x * 2; // if x == 5
+        case 9:
+            return x * 3; // if x == 9
+        default:
+            return x * 4; // other cases
+    }
+}
+```
+note that compiler can optimise few comparison conditions for ```switch``` better than that in ```if .. else```.  
+
+todo add examples
+
+
+## 2.5 aliases for imports, externs etc
+```
+use std [ stdio array string algorithm ] as use_std // definition at the beginning of the file
+
+use use_std // allows use elsewhere in the file -- generate next code in this position in the target .d file
+
+->
+
+import std.stdio;
+import std.array;
+import std.string;
+import std.algorithm;
+```
+todo add more examples
+
+
+## 2.6 code between ```dlang``` reserved words translates into target .d file without changes
+```
+...
+
+dlang
+
+// common dlang code here
+
+dlang
+
+...
+```
+
+
+## 2.7 reserved words (keywords) list
+including https://dlang.org/spec/lex.html#keywords  
+```
+abstract alias align asm assert auto 
+bool break byte 
+case cast catch char class const continue 
+dchar debug default delegate deprecated do double 
+else enum export extern 
+false final finally float for foreach foreach_reverse function 
+goto  
+if immutable import in inout int interface invariant is 
+lazy long 
+macro mixin module 
+new nothrow null 
+out override 
+package pragma private protected public pure 
+real ref return 
+scope shared static struct super switch synchronized 
+template this throw true try typeid typeof 
+ubyte uint ulong union unittest ushort 
+version void 
+wchar while with 
+
+__FILE__
+__FILE_FULL_PATH__
+__FUNCTION__
+__LINE__
+__MODULE__
+__PRETTY_FUNCTION__
+
+__gshared
+__parameters
+__rvalue
+__traits
+__vector
+
+__DATE__
+__EOF__
+__TIME__
+__TIMESTAMP__
+__VENDOR__
+__VERSION__
+
+
+[deprecated keywords] body cdouble cent cfloat creal delete idouble ifloat ireal ucent
+
+
+dlang
+use
+as
+```
+todo