Prokee Syntax Notation
Jump to navigation
Jump to search
The Prokee Syntax Notation is a notation for syntax rules used by some prokee modules.
Characteristics:
- Terminal symbols are written without quotation marks.
- There is no concatenation operator. Successive symbols are written one after the other (without a comma or space).
- There is no termination symbol, like ';' (or. '.'). The syntax rules are usually specified individually as separate string literals, which means that no termination symbol is necessary.
- For optional repetitions, "{ }" (as in EBNF) is omitted. Instead, three dots "..." are used to indicate optional continuation. Since repetition is always optional, the three points are enclosed in square brackets (see examples below).
- Any unicode characters can be used as terminal symbols. (Preferred encoding is UTF-8.)
- Spaces are not treated differently than other terminal symbols.
- If non-terminal symbols are to be used as terminal symbols, then a backslash can be prefixed to this symbol.
- As in EBNF, grouping is done with "( )" and optional parts are written within brackets "[ ]". And '|' is used for alternatives.
- Within angle brackets "<>", additional syntax specifications can be specified depending on the application.
The following table shows a comparison between EBNF and Prokee Syntax Notation.
| EBNF | Prokee Notation | Remarks | |
|---|---|---|---|
| Terminal symbols | 'a' |
a |
No single or double quotes |
| Termination symbol | 'a'; |
a |
No termination symbol |
| Concatenation | 'a', 'b', 'c' |
abc |
No spaces, no concatenation operator |
| Alternatives with '|' | 'a', 'b' | 'c' |
ab|c |
|
| Grouping | 'a', ( 'b' | 'c' ) |
a(b|c)
| |
| Optional parts | 'a', [ 'b' ] , 'c' |
a[b]c
| |
| Optional repetition, example 1 | 'a', { 'b' }, 'c' |
a[b[...]]c |
Optional repetition of the element left of [...]
|
| Optional repetition, example 2 | 'a', 'b', { 'b' }, 'c' |
ab[...]c
| |
| Optional repetition, example 3 | 'a', 'b', { 'a', 'b' }, 'c' |
(ab)[...]c
| |
| Optional repetition (with separator) | 'x', { ',', 'x' } |
x[,...] |
equal to x[(,x)[...]]
|
| Optional repetition (with separator) | 'x', { '--', 'x' } |
x[--...] |
equal to x[(--x)[...]]
|
| Optional repetition of optional element | { 'x' } |
[x]... |
equal to [x[...]]
|
