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!

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.