Crate varpulis_parser 

VPL Parser

Lexing and parsing for the VPL streaming analytics language.

This crate transforms VPL source code into an Abstract Syntax Tree (AST) that can be executed by the runtime engine.

Features

• Complete VPL grammar support
• Detailed error messages with line/column information
• Syntax hints for common mistakes
• PEG-based parsing via Pest

Modules

• pest_parser: Main parser implementation using Pest PEG grammar
• lexer: Token definitions (used for syntax highlighting)
• error: Parse error types with location information
• helpers: Parsing utility functions
• indent: Indentation handling

Quick Start

use varpulis_parser::parse;

let source = r#"
    stream Readings = SensorReading
        .where(temperature > 100)
        .emit(alert("HighTemp", "Temperature exceeded threshold"))
"#;

match parse(source) {
    Ok(program) => {
        println!("Parsed {} statements", program.statements.len());
    }
    Err(e) => {
        eprintln!("Parse error: {}", e);
    }
}

Error Handling

Parse errors include detailed location information:

use varpulis_parser::{parse, ParseError};

let result = parse("stream X form Y");  // Typo: "form" instead of "from"
if let Err(ParseError::Located { line, column, message, hint, .. }) = result {
    println!("Error at {}:{}: {}", line, column, message);
    if let Some(h) = hint {
        println!("Hint: {}", h);
    }
}

Grammar

The VPL grammar is defined in varpulis.pest and supports:

• Stream declarations with filtering, selection, windowing, and aggregation
• Event type definitions
• SASE+ pattern declarations (sequences, Kleene closures, negation)
• User-defined functions
• Configuration blocks
• Control flow (if/elif/else, for, while)
• Expressions with operators and function calls

See Also

• varpulis_core: AST types produced by the parser
• varpulis_runtime: Executing parsed programs

Re-exports

pub use error::ParseError;

pub use error::RichParseError;

pub use lexer::Token;

pub use optimizer::optimize_plan;

pub use pest_parser::parse;

Modules

error

Parse error types with source location information. Parser error types

expand

Compile-time expansion of top-level for loops in VPL source.

helpers

Helper functions for parsing literal values (durations, timestamps). Helper functions for parsing literals in LALRPOP grammar

indent

Indentation preprocessor that converts Python-style blocks to explicit markers. Indentation preprocessor for VPL

lexer

Logos-based lexer producing spanned tokens for VPL source. Lexer for VPL using Logos

optimize

AST-level constant folding optimization pass. AST-level constant folding optimization pass.

optimizer

Rule-based logical plan optimizer (filter pushdown, window merge, etc.). Rule-based logical plan optimizer

pest_parser

Pest PEG parser that transforms VPL source into an AST.