121 lines
2.7 KiB
Nim
121 lines
2.7 KiB
Nim
import
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strutils, strformat, parseutils
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type
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TokenKind* = enum
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tIdent = "ident"
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tNumber = "number"
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tDot = "dot"
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tOpenBracket = "["
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tCloseBracket = "]"
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tEof = "end of file"
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tError = "error"
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Token* = object
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case kind*: TokenKind
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of tIdent:
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name*: string
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of tNumber:
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val*: uint64
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of tError:
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errMsg: string
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else:
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discard
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Lexer* = object
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tok*: Token
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input: string
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pos: int
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Parser* = object
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lexer: Lexer
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NodeKind* = enum
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Ident
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Number
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Dot
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ArrayAccess
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Error
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Node* = ref object
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case kind*: NodeKind
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of Dot:
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objVal*, field*: Node
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of ArrayAccess:
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arrayVal*, index*: Node
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of Ident:
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name*: string
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of Number:
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numVal*: uint64
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of Error:
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errMsg*: string
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func advance(lexer: var Lexer) =
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if lexer.pos >= lexer.input.len:
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lexer.tok = Token(kind: tEof)
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else:
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let nextChar = lexer.input[lexer.pos]
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case nextChar
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of IdentStartChars:
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lexer.tok = Token(kind: tIdent)
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lexer.pos = parseIdent(lexer.input, lexer.tok.name, lexer.pos)
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of Whitespace:
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lexer.pos = skipWhitespace(lexer.input, lexer.pos)
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advance lexer
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of Digits:
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lexer.tok = Token(kind: tNumber)
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lexer.pos = parseBiggestUInt(lexer.input, lexer.tok.val, lexer.pos)
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of '[':
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lexer.tok = Token(kind: tOpenBracket)
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inc lexer.pos
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of ']':
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lexer.tok = Token(kind: tCloseBracket)
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inc lexer.pos
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of '.':
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lexer.tok = Token(kind: tDot)
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inc lexer.pos
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else:
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lexer.tok = Token(
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kind: tError,
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errMsg: &"Unexpected character '{nextChar}' at position {lexer.pos}")
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func init*(T: type Lexer, src: string): Lexer =
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result.input = src
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result.pos = 0
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advance result
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func init*(T: type Parser, src: string): Parser =
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Parser(lexer: Lexer.init(src))
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func expr(parser: var Parser): Node =
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template unexpectedToken =
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return Node(kind: Error, errMsg: &"Unexpected {parser.lexer.tok.kind} token")
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case parser.lexer.tok.kind
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of tIdent:
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result = Node(kind: Ident, name: parser.lexer.tok.name)
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of tNumber:
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return Node(kind: Number, numVal: parser.lexer.tok.val)
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else:
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unexpectedToken
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advance parser.lexer
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case parser.lexer.tok.kind
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of tOpenBracket:
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advance parser.lexer
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result = Node(kind: ArrayAccess, arrayVal: result, index: parser.expr)
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if parser.lexer.tok.kind != tCloseBracket:
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unexpectedToken
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else:
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advance parser.lexer
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of tDot:
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advance parser.lexer
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return Node(kind: Dot, objVal: result, field: parser.expr)
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else:
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discard
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func parse*(input: string): Node =
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var p = Parser.init(input)
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p.expr
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