Crate parlex_calc 

parlex-calc

A small demonstration crate built on parlex, providing a complete, minimal example of a lexer–parser pipeline for a calculator language.

This crate showcases how to connect a CalcLexer and CalcParser using token spans and a shared symbol table. It’s intended for educational and testing purposes rather than production use.

Overview

The parlex-calc crate defines the following components:

• lexer — a tokenizing module that converts raw input into a stream of CalcToken items, each annotated with a [Span] indicating its position in the source text.
• parser — a grammar-based parser that consumes lexer tokens to produce an abstract syntax tree (AST) or evaluate expressions directly.
• symtab — a symbol table abstraction (SymTab) that manages variable bindings and supports expression evaluation.
• token — shared token definitions, including CalcToken, TokenValue, and TokenID.

Example

use try_next::{IterInput, TryNextWithContext};
use parlex::span;
use parlex_calc::{CalcParser, CalcToken, SymTab, TokenID, TokenValue};

// Input source string
let source = "a = 1 + 2 * 3";

// Initialize parser

let mut symtab = SymTab::new();
let input = IterInput::from(source.bytes());
let mut parser = CalcParser::try_new(input).unwrap();

// Run the lexer–parser pipeline
let Ok(Some(token)) = parser.try_next_with_context(&mut symtab) else {panic!("expected token")};
assert!(matches!(
    token,
    CalcToken {
        token_id: TokenID::Stat,
        span: span!(0, 0, 0, 13),
        value: TokenValue::Number(7)
    }
));

Modules

• lexer — lexical analysis (tokenization)
• parser — grammar-based parsing
• symtab — symbol table and evaluation context
• token — token definitions and span utilities

Re-exports

To simplify integration, the crate re-exports its main entry points:

CalcLexer, CalcLexerDriver, CalcParser, CalcParserDriver,
SymTab, SymTabError, CalcToken, TokenValue, TokenID

These are the primary types needed to embed parlex-calc in tests, examples, or small interpreters.

Re-exports

pub use lexer::CalcLexer;

pub use lexer::CalcLexerDriver;

pub use parser::parser_data::TokenID;

pub use parser::CalcParser;

pub use parser::CalcParserDriver;

pub use symtab::SymTab;

pub use symtab::SymTabError;

pub use token::CalcToken;

pub use token::TokenValue;

Modules

lexer

Calculator Lexer

parser

Calculator Parser

symtab

A minimal, flat symbol table built on indexmap::IndexMap.

token

Calculator Tokens