iec2peg.py

# IEC grammar language to pyPEG compiler

from pyPEG import parse

import re

r = re.compile

import fileinput


def comment():
    return r(r"\#.*")


terminal_symbol = r(r"\$?('.*?'" + r'|".*?")')
non_terminal_symbol = r(r"[a-z_][a-z0-9_]*")


def regex():
    return "<", r(r"((\\\>)|[^>])+"), ">"


def production():
    return non_terminal_symbol, "::=", [alternation, concat], ";"


def concat():
    return (
        -2,
        [regex, terminal_symbol, non_terminal_symbol, parentheses, closure, option],
    )


def _extended_structure():
    return [
        alternation,
        regex,
        terminal_symbol,
        non_terminal_symbol,
        parentheses,
        closure,
        option,
    ]


_S = -2, _extended_structure


def parentheses():
    return "(", _S, ")"


def closure():
    return "{", _S, "}"


def option():
    return "[", _S, "]"


def alternation():
    return concat, -2, ("|", concat)


iecpeg = -2, production

files = fileinput.input("iec.grammar")
ast = parse(iecpeg, files, True, comment)


def genPEG(obj, genparens=True):
    result = ""
    if type(obj) == type([]):
        for e in range(len(obj)):
            text = genPEG(obj[e])
            m = re.compile(r"def [a-z_0-9]+\(\)\:").match(text)
            if e == 0:
                if not m and len(obj) > 1 and genparens:
                    result += "("
            result += text
            if e < len(obj) - 1:
                if m:
                    result += "\n"
                else:
                    result += ", "
            else:
                if not m and len(obj) > 1 and genparens:
                    result += ")"
    elif type(obj) == type((None,)):
        name = obj[0]
        if name == "production":
            result += "def " + obj[1][0] + "(): return "
            for e in range(1, len(obj[1])):
                result += genPEG(obj[1][e])
                if e < len(obj[1]) - 1:
                    result += ", "
        elif name == "regex":
            result += 're.compile(r"' + obj[1][0] + '")'
        elif name == "parentheses":
            for e in range(1, len(obj)):
                result += genPEG(obj[e])
        elif name == "closure":
            result += "-1, "
            for e in range(1, len(obj)):
                result += genPEG(obj[e])
        elif name == "option":
            result += "0, "
            for e in range(1, len(obj)):
                result += genPEG(obj[e])
        elif name == "alternation":
            result += "["
            for e in range(1, len(obj)):
                result += genPEG(obj[e], False)
            result += "]"
        elif name == "concat":
            for e in range(1, len(obj)):
                result += genPEG(obj[e])
    elif type(obj) == type(""):
        if obj[0] == "$":
            result += "keyword(" + obj[1:] + ")"
        else:
            result += obj
    return result


# print ast
print("import re\nfrom pyPEG import keyword\n")
print(genPEG(ast))