Nasal-Interpreter/README.md

# Nasal-- Interpreter

# Nasal

Nasal is a script language that used in FlightGear.

There is a Nasal console in FlightGear but sometimes it is not so easy for every developer to use.

So this is an interpreter for Nasal written by C++.

The interpreter is still in development.Anyone who interested in this could also join us!

# Issue in nasal console in flightgear

When calling a function without a ';' ,the console does not find the error.But in nasal's grammar this seems really wrong.

So in my interpreter,if you call the function only without a ';' behind it,you will get a piece of error information!

# Now complete all types

var: int   float   double   std::string   char   long long int

NasalList: array in nasal []

  append
  
  setsize
  
  subvec
  
  pop
  
  sort

NasalHash: Hash in nasal {}

  append
  
  delete
  
  contains

  keys
  
  # Now complete Lexical Analysis!
  
  What it looks like?
  
( Identifier  | engineTimer )

( Operator    | . )

( Identifier  | start )

( Operator    | ( )

( Operator    | ) )

( Operator    | ; )

( ReserveWord | print )

( Operator    | ( )

( String      | "Engine started" )

( Operator    | ) )

( Operator    | ; )

( Operator    | } )

( ReserveWord | var )

( Identifier  | stopEngine )

( Operator    | = )

( ReserveWord | func )

( Operator    | ( )

( Operator    | ) )

( Operator    | { )

( Identifier  | props )

( Operator    | . )

( Identifier  | getNode )

( Operator    | ( )

( String      | "/" )

( Operator    | , )

( Number      | 1 )

( Operator    | ) )

( Operator    | . )

( Identifier  | setValue )

( Operator    | ( )

( String      | "/controls/engines/engine/started" )

( Operator    | , )

( Number      | 0 )

( Operator    | ) )

( Operator    | ; )

( Identifier  | props )

( Operator    | . )

( Identifier  | getNode )

( Operator    | ( )

( String      | "/" )

( Operator    | , )

( Number      | 1 )

( Operator    | ) )

( Operator    | . )

( Identifier  | setValue )

( Operator    | ( )

( String      | "/fdm/jsbsim/external_reactions/engine/magnitude" )

( Operator    | , )

( Number      | 0 )

( Operator    | ) )

( Operator    | ; )

( Identifier  | props )

( Operator    | . )

( Identifier  | getNode )

( Operator    | ( )

( String      | "/" )

( Operator    | , )

( Number      | 1 )

( Operator    | ) )

( Operator    | . )

( Identifier  | setValue )

( Operator    | ( )

( String      | "/systems/electrical/e-tron/switch/bat-fwd-eng" )

( Operator    | , )

( Number      | 0 )

( Operator    | ) )

( Operator    | ; )

( Identifier  | props )

( Operator    | . )

( Identifier  | getNode )

( Operator    | ( )

( String      | "/" )

( Operator    | , )

( Number      | 1 )

( Operator    | ) )

( Operator    | . )

( Identifier  | setValue )

( Operator    | ( )

( String      | "/systems/electrical/e-tron/switch/bat-bwd-eng" )

( Operator    | , )

( Number      | 0 )

( Operator    | ) )

( Operator    | ; )

( Identifier  | engineTimer )

( Operator    | . )

( Identifier  | stop )

( Operator    | ( )

( Operator    | ) )

( Operator    | ; )

( ReserveWord | print )

( Operator    | ( )

( String      | "Engine stopped" )

( Operator    | ) )

( Operator    | ; )

( Operator    | } )

This is what it outputs.

# Now with var_stack and function_stack

By printing the two stacks you can see how vars and functions change!

[long long int]a:1

[double]b:3.14

[string]c:"hello world!"

function:swap

function:__main

function:hello

# Now the parser can...

recognize all these things...

    print("a",e);
    var e=1;
    var e="str";
    var e=[];
    var e={};
    var e=e[0];
    var e=e.e;
    var e=e(0);
    var e=e();
    var e=e[e()];
    var e=[1,e,1,e,1];
    var e=[e,e,e,e];
    var e={e:1,e:2,e:3};
    var e=e[e.e];
    e=1;
    e="str";
    e=[];
    e={};
    e=e[0];
    e=e.e;
    e=e(0);
    e=e();
    e=e[e()];
    e=[1,e,1,e,1];
    e=[e,e,e,e];
    e={e:1,e:2,e:3};
    e=e[e.e];
    e=e.e();
    var e={
        e:1,
        e:func(){},
        e:func(e,e){},
        e:func(){
            e;
            e;
        },
        e:func(e,e){
            e;
            e;
        }
    };
    var e=func(){}
    var e=func(e,e){}
    var e=func(){e;e;}
    var e=func(e,e){e;e;}
    var e=func(e,e,e,e,e){
        e=1;
        e=e[0];
        e=e(e,e,e);
        return e;
    }
    e+=e;
    e-=e;
    e*=e;
    e/=e;
    e~=e;
    e+=(e-e)*(e+(e/e));
    e=e-e*(!2);
    var e=e[0]~e[1]~e[2];
    var e={
        e:[],
        e:{}
    };
    return {};
    return [];
    return {parent:[e]};
    var e=0o7103;#Oct
    var e=0x55aa;#Hex
    var e=e/e;
    var e=e[e/e];
    var e=-e;
    var e=-1;
    var e=func(e){e;}
    var e={e:e/e,e:1};
    e= e.e(e,1).e()+e*e.e(e.e*e/180);
    if(!e.e)e;
    var e=e.e("str",1).e()*e.e("str",1).e*0.001;
    e.e("str",1).e("str",e-e);
    e.e(e("str",e.e()/2880)~"str");
    var e=func(){e;};


# The structure of basical elements is...

class var;

class nasal_hash;//forward declaration

struct nasal_list_unit;

class nasal_list;

struct nasal_hash_unit;

class nasal_hash;

struct token_unit;

struct parameter;

class func;

class var_stack;

var_stack nasal_var_stack;

class func_stack;

func_stack nasal_func_stack;

class token_list;

token_list nasal_lexer;

class parse;

parse nasal_parser;

#include "nasal_lexer.h"

main();

# Push down automata

After many times of failure,i finally try to use PDA to do the parse work.