String Engine

String Engine is the textual backend in Lc.

It is suitable for:

• command-oriented runtimes,
• script-like processing layers,
• language-front execution stages,
• text transformation and compilation steps.

Runtime flow

1. Input stored in INPUT string.
2. Parser returns []ParsedNode.
3. Parsed nodes stored in PARSED []ParsedNode.
4. Runtime dispatches command handlers by ParsedNode.Switch.
5. Handlers write to UEP.Generator.

Parser options

All parser results has automatic __prev / __next node references.

Parser1 (grammar-first)

Use when you need:

• regex grammar matching,
• multiline continuation support,
• bracket-balance parsing,
• capture-group metadata extraction.

Parser2 (line-command parser)

Use when lines follow command args shape.

• command -> Switch
• rest of line -> metadata args

Lexer (token-first)

Use when tokenization is a separate concern:

• ordered regexp2 matching,
• named metadata groups,

Command contract

Registration:

• NewCommandString(cmdSwitch, handler, doc)

Handler signature:

• func(*engine.StringEngine, stringParsing.ParsedNode) error

Recommended behavior:

• validate metadata early,
• keep side effects explicit,
• write deterministic output to known pipeline points,
• return typed/context-rich errors.

Metadata discipline

Typical metadata keys:

• parser-defined capture groups,
• __raw,
• __value (lexer),
• __prev, __next.

In large projects, treat metadata as schema:

• define key constants centrally,
• version key contracts with parser evolution.

Output strategy

Write:

• Generator.AddString(...)
• Generator.AddStrings(...)

Read:

• Generator.GetStringArrRes()
• Generator.GetStringRes(sep)

Use explicit pipeline points to separate runtime phases.