121 lines
1.7 KiB
Go
121 lines
1.7 KiB
Go
package parser
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// TokenType represents the type of a token
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type TokenType int
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const (
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// Literals
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IDENT TokenType = iota
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NUMBER
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STRING
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TRUE
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FALSE
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NIL
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// Operators
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ASSIGN // =
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PLUS // +
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MINUS // -
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STAR // *
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SLASH // /
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DOT // .
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// Comparison operators
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EQ // ==
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NOT_EQ // !=
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LT // <
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GT // >
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LT_EQ // <=
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GT_EQ // >=
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// Delimiters
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LPAREN // (
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RPAREN // )
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LBRACE // {
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RBRACE // }
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LBRACKET // [
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RBRACKET // ]
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COMMA // ,
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// Keywords
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VAR
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IF
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THEN
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ELSEIF
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ELSE
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END
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ECHO
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FOR
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WHILE
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IN
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DO
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// Special
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EOF
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ILLEGAL
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)
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// Token represents a single token
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type Token struct {
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Type TokenType
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Literal string
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Line int
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Column int
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}
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// Precedence levels for Pratt parsing
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type Precedence int
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const (
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_ Precedence = iota
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LOWEST
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EQUALS // ==, !=
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LESSGREATER // >, <, >=, <=
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SUM // +, -
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PRODUCT // *, /
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PREFIX // -x, !x
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MEMBER // table[key], table.key
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CALL // function()
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)
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// precedences maps token types to their precedence levels
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var precedences = map[TokenType]Precedence{
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EQ: EQUALS,
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NOT_EQ: EQUALS,
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LT: LESSGREATER,
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GT: LESSGREATER,
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LT_EQ: LESSGREATER,
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GT_EQ: LESSGREATER,
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PLUS: SUM,
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MINUS: SUM,
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SLASH: PRODUCT,
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STAR: PRODUCT,
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DOT: MEMBER,
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LBRACKET: MEMBER,
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}
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// lookupIdent checks if an identifier is a keyword
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func lookupIdent(ident string) TokenType {
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keywords := map[string]TokenType{
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"var": VAR,
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"true": TRUE,
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"false": FALSE,
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"nil": NIL,
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"if": IF,
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"then": THEN,
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"elseif": ELSEIF,
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"else": ELSE,
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"end": END,
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"echo": ECHO,
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"for": FOR,
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"while": WHILE,
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"in": IN,
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"do": DO,
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}
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if tok, ok := keywords[ident]; ok {
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return tok
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}
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return IDENT
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}
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