Extended BNF
- BNFはoptionalな項目や繰り返しを記述するのがダルい
- EBNFでは：
- optional:
signed number = [ sign ], number ;- BNFだと
<signed-number> ::= <sign> <number> | <number>となる
- BNFだと
- repeat:
number = { digit } ;- BNFだと
<number> ::= <digit> | <number> <digit>となる
- BNFだと
- optional:
| Usage | Notation | Alternative | Meaning |
|---|---|---|---|
| definition | = | ||
| concatenation | , | ||
| termination | ; | . | |
| alternation | | | / or ! | |
| optional | [ … ] | (/ … /) | none or once |
| repetition | { … } | (: … :) | none or more |
| grouping | ( … ) | ||
| terminal string | ” … ” | ’ … ‘ | |
| comment | (* … *) | ||
| special sequence | ? … ? | ||
| exception | - | ||
| Wikipediaより |