Question 1

How to parse JSON at compile time with Pegged?

Accepted Answer

Use the pre-defined JSON grammar included with Pegged: mix it in and call it with a string at compile time using 'enum parseTree = JSONGrammar(yourString);'. This allows for static analysis or code generation based on JSON input without runtime overhead.

Question 2

Is Pegged better than writing a parser by hand in D?

Accepted Answer

For development speed and maintainability, Pegged excels with its declarative syntax, but hand-written parsers may offer better runtime performance and finer control. Pegged's abstraction layers can introduce template bloat, so benchmark for critical paths.

Question 3

Can Pegged handle left recursion at compile time?

Accepted Answer

No, left recursion is fully supported only at runtime. The README specifies that left recursion is handled during runtime parsing, so compile-time parsing of left-recursive grammars will fail or require workarounds.

Question 4

How to add custom actions to parse tree nodes?

Accepted Answer

Attach semantic actions by defining delegates or functions and associating them with rules in the grammar. Refer to the 'Semantic Actions' wiki page for examples on processing nodes during parsing, such as transforming matches on-the-fly.

Question 5

Pegged vs other D parsing libraries like dparser: which to choose?

Accepted Answer

Pegged uses PEG syntax and supports compile-time parsing, ideal for code generation and DSLs. dparser is a traditional parser generator focused on runtime. Choose Pegged for metaprogramming needs, but dparser might be simpler for runtime-only tasks.

Question 6

How to handle whitespace in grammars?

Accepted Answer

By default, Pegged does not silently consume spaces, following standard PEG behavior. Use the '< ' arrow instead of '<-' in rules to make them space-sensitive, as shown in the Arithmetic example where operators skip spaces.

Pegged

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