compiler

StandardQL Parser

A Haskell implementation of the StandardQL language parser for the Swiss Federal Register of Buildings and Dwellings (RegBL).

Overview

StandardQL is a declarative constraint language designed for expressing quality rules in the RegBL system. This parser:

• Implements the full StandardQL grammar as specified in the BNF
• Immediately elaborates condition syntax into expressions
• Produces a JSON-serializable AST for Java interoperability
• Handles operator precedence correctly (LL(2) parser)

Building

cabal build

Testing

cabal test

Usage

Command Line

# Parse from stdin
echo "GSTAT = 1007 WHERE GABBJ NOT NULL" | cabal run standardql-compiler

# Parse from file
cabal run standardql-compiler -- -i rule.sql -o output.json

# Pretty print AST
cabal run standardql-compiler -- -i rule.sql -p

# Validate only (no output)
cabal run standardql-compiler -- -i rule.sql -v

As a Library

import StandardQL
import Data.Aeson (encode)

-- Parse a program
case parseProgram "GSTAT = 1007" of
  Left err -> putStrLn $ errorBundlePretty err
  Right program -> print $ encode program

Language Features

Basic Expressions

-- Simple comparisons
GSTAT = 1007
x > 5
name != "test"

-- Arithmetic
x + 1 = 10
price * 1.2 < 100

-- Logical operators
x > 0 AND y < 10
status = 1 OR status = 2

Conditions (Syntactic Sugar)

-- NULL checks
GABBJ NULL          -- elaborates to: GABBJ = NULL
GABBJ NOT NULL      -- elaborates to: GABBJ != NULL

-- BETWEEN
x BETWEEN 1 AND 10  -- elaborates to: x >= 1 AND x <= 10

-- IN
x IN (1|2|3)        -- elaborates to: x = 1 OR x = 2 OR x = 3
x IN (1-5)          -- elaborates to: x >= 1 AND x <= 5
x IN (1|5-10|20)    -- mixed ranges

-- NOT IN
x NOT IN (1|2)      -- elaborates to: NOT (x = 1 OR x = 2)

MATCHES Operator

The MATCHES operator creates a closure where the identifier is implicitly passed as the first argument to function calls:

LPARZ MATCHES (LENGTH <= 12)
-- elaborates to: LENGTH(LPARZ) <= 12

name (LENGTH > 0 AND < 100)
-- elaborates to: LENGTH(name) > 0 AND LENGTH(name) < 100

WHERE Clauses

GSTAT = 1007 WHERE GABBJ NOT NULL
-- Statement with a filter condition

Function Calls

COUNT(WSTAT) > 0
SUM(amount) <= 1000
LENGTH(name) BETWEEN 1 AND 50

Examples from RegBL

-- BQ9980: Building status must be "demolished" when demolition year is set
GSTAT = 1007 WHERE GABBJ NOT NULL

-- BQ7447: Construction year must not be after demolition year
GABBJ>=GBAUJ
WHERE GBAUJ NOT NULL AND GABBJ NOT NULL

AST Structure

The parser produces a JSON-serializable AST with the following main types:

• Program: Top-level container
• Statement: Simple or filtered (with WHERE)
• Expression: Binary operations, function calls, identifiers, values
• Value: Numbers, strings, or NULL
• Identifier: Variable/attribute names
• FunctionCall: Function name with arguments

Implementation Notes

1. Condition Elaboration: All condition syntax is immediately transformed into equivalent expressions during parsing
2. Operator Precedence: Follows standard precedence (multiplication before addition, AND before OR, etc.)
3. Reserved Words: AND, OR, IS, NOT, NULL, BETWEEN, IN, MATCHES, WHERE cannot be used as identifiers
4. Case Sensitivity: Keywords are case-insensitive, identifiers are case-sensitive
5. Comments: Supports -- line comments and {- -} block comments