"GDPeg" Parsing Expression Grammar for GDScript, GodotEngine 4

It is implementation of Parsing Expression Grammar.

If you want to parse GDScript on GDScript, so Check GDScript Parsers!

for Godot Engine 3

See this repository

Help

Document

How to Use

Text Notation

func number( s:String ):
    return { "number": int(s) }

func binop_non_folding( group:Array ):
    var node = group[0]
    for i in range( 1, len( group ), 2 ):
        node = { "op": group[i+0], "left": node, "right": group[i+1] }
    return node

func show_tree( leaf:Dictionary ) -> String:
    if leaf.has("op"):
        return "(%s %s %s)" % [
            leaf.op,
            show_tree( leaf.left ),
            show_tree( leaf.right )
        ]
    else:
        return leaf.number

func _ready( ):
    var parser:GDPeg.PegTree = GDPeg.generate( """
        expr < term ( ~\"[+\\-]\" term )* $
        term < factor ( ~\"[*/]\" factor )*
        factor < number / \"(\" expr \")\"
        number <~ ~\"[0-9]+\"
    """, {
        "expr": self.binop_non_folding
    ,	"term": self.binop_non_folding
    ,	"number": self.number
    } )
    var result:GDPeg.PegResult = parser.parse( "1+2+3*4+5", 0 )

    print( result.accept )
    if result.accept:
        print( result.capture[0] )
        print( show_tree( result.capture[0] ) )

Instance Notation

結構柔軟に書ける。

func number( s:String ):
    return { "number": int(s) }

func binop( root:Array, group:Array ):
    return { "op": group[0], "left": root[0], "right": group[1] }

func show_tree( leaf:Dictionary ) -> String:
    if leaf.has("op"):
        return "(%s %s %s)" % [
            leaf.op,
            show_tree( leaf.left ),
            show_tree( leaf.right )
        ]
    else:
        return leaf.number

func _ready( ):
    var number:GDPeg.PegTree = GDPeg.capture( GDPeg.regex( "[0-9]+" ), funcref( self, "number" ) )
    var term:GDPeg.PegTree = GDPeg.capture_folding(
        GDPeg.concat([
            number,
            GDPeg.greedy(
                GDPeg.capture_group(
                    GDPeg.concat([
                        GDPeg.capture(
                            GDPeg.select([
                                GDPeg.literal( "*" ),
                                GDPeg.literal( "/" ),
                                GDPeg.literal( "%" ),
                            ])
                        ),
                        number,
                    ])
                ),
                0
            )
        ]),
        self.binop
    )
    var expr:GDPeg.PegTree = GDPeg.capture_folding(
        GDPeg.concat([
            term,
            GDPeg.greedy(
                GDPeg.capture_group(
                    GDPeg.concat([
                        GDPeg.capture(
                            GDPeg.select([
                                GDPeg.literal( "+" ),
                                GDPeg.literal( "-" ),
                            ])
                        ),
                        term,
                    ])
                ),
                0
            )
        ]),
        self.binop
    )
    var parser:GDPeg.PegTree = expr
    var result:GDPeg.PegResult = parser.parse( "1+2+3*4+5", 0 )

    print( result.accept )
    print( result.capture[0] )

    print( show_tree( result.capture[0] ) )

TODO

• 高速化
• Lambda式使うように書き換える

License

MIT License

Author

あるる / きのもと 結衣 @arlez80