r - ast.go

     1  // Package r implements an R tokeniser and parser.
     2  package r
     3  
     4  import (
     5  	"vimagination.zapto.org/parser"
     6  )
     7  
     8  // File represents a parsed R file.
     9  type File struct {
    10  	Statements []Expression
    11  	Comments   Comments
    12  	Tokens     Tokens
    13  }
    14  
    15  // Parse parses R input into AST.
    16  func Parse(t Tokeniser) (*File, error) {
    17  	r, err := newRParser(t)
    18  	if err != nil {
    19  		return nil, err
    20  	}
    21  
    22  	f := new(File)
    23  	if err = f.parse(&r); err != nil {
    24  		return nil, err
    25  	}
    26  
    27  	return f, nil
    28  }
    29  
    30  func (f *File) parse(r *rParser) error {
    31  	s := r.NewGoal()
    32  
    33  	for s.AcceptRunWhitespace() != parser.TokenDone {
    34  		r.AcceptRunWhitespaceNoComment()
    35  
    36  		var e Expression
    37  
    38  		s = r.NewGoal()
    39  
    40  		if err := e.parse(&s); err != nil {
    41  			return r.Error("File", err)
    42  		}
    43  
    44  		f.Statements = append(f.Statements, e)
    45  
    46  		r.Score(s)
    47  		r.AcceptRunWhitespaceNoNewLine()
    48  
    49  		if !r.AcceptToken(parser.Token{Type: TokenExpressionTerminator, Data: ";"}) && !r.Accept(TokenLineTerminator) && r.Peek().Type != parser.TokenDone {
    50  			return r.Error("File", ErrMissingStatementTerminator)
    51  		}
    52  
    53  		s = r.NewGoal()
    54  	}
    55  
    56  	f.Comments = r.AcceptRunWhitespaceComments()
    57  	f.Tokens = r.ToTokens()
    58  
    59  	return nil
    60  }
    61