Nelumbo

Bootstrap grammar

Level: Java core. Always present, nothing to import.

KnowledgeBase.BASE, the knowledge base every file starts from, begins with a small grammar written in Java (KnowledgeBase.initBase()). It holds just enough syntax to read lang.nl. Nothing else is in BASE. Every other construct, including most of the syntax you write, arrives through import.

What the Java core declares

Construct Shape Re-declared in lang.nl as
File begin-of-file, top-level statements separated by newlines, end-of-file Namespace ::= <BEGINOFFILE> ... <ENDOFFILE>
Import import a.b.c, d.e Root ::= "import" ...
Type declaration T :: S1, S2, T<A> :: S, optional #GROUP Root ::= ... :: ...
Pattern declaration private? T ::= P #N @qualified.Class, ... Root ::= ... ::= ...
Named pattern pattern N ::= P PatternPart ::= "pattern" <NAME> ::= <PATTERNS>
Token patterns a NAME, OPERATOR, SEMICOLON, SINGLEQUOTE, COMMA or STRING token as a literal Pattern ::= <NAME>, <STRING>, ...
Alternation `<(> P < > Q <)>`
Repetition <(> P <,> sep <)*>, <(> P <)+> Pattern ::= ...
Optional <(> P <)?> Pattern ::= ...
Sequence ( P ), [ P ], { P }, and the connected group <[> P <]> Pattern ::= ...
Type hole <T>, <T#100>, <hidden T>, <visible T> Pattern ::= "<" ... <Type#100> ... ">"
Named-pattern hole <N> Pattern ::= "<" <PatternPart#100> ">"

Besides these patterns the core registers one type per token type (NAME, NUMBER, STRING, ...) and a fixed set of predefined types (Type.predefined()): NATIVE, Object, Type, World, Namespace, Function, Literal, Root, Boolean, Variable, Functor, PatternPart, Pattern, Struct, Collection, Set, List and Lambda. The Java classes behind the reasoner and the collections refer to these types. Being registered does not give them any syntax: values, operators and statements for Boolean, Function or Set only exist once the .nl file that declares them is imported.

What happens next

import nelumbo.lang loads lang.nl. It declares the constructs above again, as ordinary ::= patterns bound to Java classes with @, and adds the rest of the nelumbo.lang syntax: variable declarations, ::> transformations, { } scope blocks, the <Variable> hole and generic parenthesisation. From then on files are parsed with those declarations.

The other levels come in the same way. nelumbo.logic imports nelumbo.lang, nelumbo.integers imports nelumbo.logic, and the other packages import nelumbo.integers.

See also