Converting EBNF to BNF

Be warned: EBNF as it's listed in the ISO standard also includes exceptions to syntactic rules, which do not have a BNF equivalent. The conversion given by 500 - Internal Server Error only works for the portion of EBNF which overlaps with RBNF/ABNF.

See this page.^🕗 It contains instructions for each production that needs to be converted:

From EBNF to BNF

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For building parsers (especially bottom-up) a BNF grammar is often better, than EBNF. But it's easy to convert an EBNF Grammar to BNF:

• Convert every repetition { E } to a fresh non-terminal X and add

  X = ε | X E.
  

• Convert every option [ E ] to a fresh non-terminal X and add

  X = ε | E.
  

  (We can convert X = A [ E ] B. to X = A E B | A B.)

• Convert every group ( E ) to a fresh non-terminal X and add

  X = E.
  

• We can even do away with alternatives by having several productions with the same non-terminal.

  X = E | E'. becomes X = E. X = E'.