FancyPars

[Rory McGuire via Digitalmars-d-announce]

Nice one, thanks for the info.

I just used Pegged to generate an API for a JSON REST service at compile
time so I'm still geeking out about the power of D at compile time, but I'm
always interested in parsers.

On Mon, Sep 14, 2015 at 10:50 AM, Bastiaan Veelo via Digitalmars-d-announce
<digitalmars-d-announce at puremagic.com> wrote:

> On Monday, 6 July 2015 at 09:22:51 UTC, Per Nordlöw wrote:
>
>>
>> How does its design and use differ from Pegged?
>>
>
> FWIW, this is what I learned from my first acquaintance with FancyPars
> (the OP having signalled not to be available for questions). My conclusions
> may be wrong though.
>
> Running dub produces a vibe.d web server demonstrating the capabilities of
> FancyPars. This was a bit confusing at first because being a web-app seemed
> central to the design of FancyPars, but I think it is not. Anyway, the
> first page shows a large edit field containing an example grammar, and a
> button "Generate AST". Clicking this button brings up the second page
> containing D code for the lexer and parser for the given grammar, type
> definitions for the nodes of the AST, as well as code for printing the AST.
>
> Understanding the source of FancyPars is challenging because the core
> source, example vibe.d application source and supporting code, as well as
> generated lexer/parser code are all contained in the same directory and
> committed in the repository.
>
> The syntax for the grammar definition is different from Pegged, and seems
> to be inspired by D. It supports a hierarchical structure. It looks
> powerful, but is undocumented. The example grammar looks like this:
>
> ASTNode {
>     Identifier @internal {
>         [a-zA-Z_][] identifier
>     }
>
>     Group @parent {
>         Identifier name, ? "@" : Identifier[] annotations : "@", "{",
>             PatternElement[] elements : "," / Group[] groups,
>              "}"
>     }
>
>     PatternElement @internal {
>
>         AlternativeElement @noFirst {
>             PatternElement[] alternatives : "/"
>         }
>
>         LexerElement {
>
>             StringElement {
>                 "\"", char[] string_, "\""
>             }
>
>             NamedChar {
>                 "char", ? "[]" : bool isArray, Identifier name
>             }
>
>             CharRange @internal {
>                 char rangeBegin,  ? "-" : char RangeEnd
>             }
>
>             RangeElement {
>                 "[", CharRange[] ranges, "]"
>             }
>
>             LookbehindElement {
>                 "?lb", "(", StringElement str, ")"
>             }
>
>             NotElement {
>                 "!", LexerElement ce
>             }
>
>         }
>
>         NamedElement {
>             Identifier type,  ? "[]" : bool isArray, Identifier name,
>             ? bool isArray : ? ":" : StringElement lst_sep
>         }
>
>         ParenElement {
>             "(", PatternElement[] elements : ",", ")"
>         }
>
>         FlagElement {
>             "bool", Identifier flag_name
>         }
>
>         QueryElement {
>             "?", "bool", Identifier flag_name, ":", PatternElement elem
>         }
>
>         OptionalElement {
>             "?", LexerElement[] ce : ",", ":", PatternElement elem
>         }
>
>     }
> }
>
>
> Its announced support for left-recursion is interesting, and I may decide
> to play a bit further with it. My objective would be to see if an Extended
> Pascal to D translating compiler would be feasible.
>
> Cheers,
> Bastiaan Veelo.
>
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