56 lines
1.5 KiB
Lua
56 lines
1.5 KiB
Lua
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package.path = package.path .. ";../?.lua"
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local pg = require "parser-gen"
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local peg = require "peg-parser"
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local errs = {errMissingThen = "Missing Then"}
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pg.setlabels(errs)
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local grammar = pg.compile([[
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program <- stmtsequence !.
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stmtsequence <- statement (';' statement)*
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statement <- ifstmt / repeatstmt / assignstmt / readstmt / writestmt
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ifstmt <- 'if' exp 'then'^errMissingThen stmtsequence elsestmt? 'end'
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elsestmt <- ('else' stmtsequence)
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repeatstmt <- 'repeat' stmtsequence 'until' exp
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assignstmt <- IDENTIFIER ':=' exp
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readstmt <- 'read' IDENTIFIER
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writestmt <- 'write' exp
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exp <- simpleexp (COMPARISONOP simpleexp)*
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COMPARISONOP <- '<' / '='
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simpleexp <- term (ADDOP term)*
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ADDOP <- [+-]
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term <- factor (MULOP factor)*
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MULOP <- [*/]
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factor <- '(' exp ')' / NUMBER / IDENTIFIER
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NUMBER <- '-'? [0-9]+
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KEYWORDS <- 'if' / 'repeat' / 'read' / 'write' / 'then' / 'else' / 'end' / 'until'
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RESERVED <- KEYWORDS ![a-zA-Z]
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IDENTIFIER <- !RESERVED [a-zA-Z]+
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HELPER <- ';' / %nl / %s / KEYWORDS / !.
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SYNC <- (!HELPER .)*
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]], _, true)
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local errors = 0
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local function printerror(desc,line,col,sfail,trec)
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errors = errors+1
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print("Error #"..errors..": "..desc.." on line "..line.."(col "..col..")")
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end
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local function parse(input)
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errors = 0
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result, errors = pg.parse(input,grammar,printerror)
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return result, errors
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end
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if arg[1] then
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-- argument must be in quotes if it contains spaces
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res, errs = parse(arg[1])
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peg.print_t(res)
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peg.print_r(errs)
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end
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local ret = {parse=parse}
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return ret
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