using OpenLanguage.SpreadsheetML.Formula;
// Parse an Excel formula
Ast.Node formula = FormulaParser.Parse("=SUM(A1:A10) * 2");
// Access the AST
Console.WriteLine($"Reconstructed: {formula.ToString()}");
// Try parsing with error handling
Ast.Node? maybeFormula = FormulaParser.TryParse("=INVALID_SYNTAX(");
if (maybeFormula == null)
{
Console.WriteLine("Parse failed - invalid syntax");
}
Field Instruction Processing
using OpenLanguage.WordprocessingML.FieldInstruction;
using OpenLanguage.WordprocessingML.FieldInstruction.Typed;
// Create a field instruction
var instruction = new FieldInstruction("MERGEFIELD");
instruction.Arguments.Add(new FieldArgument(FieldArgumentType.Identifier, "FirstName"));
instruction.Arguments.Add(new FieldArgument(FieldArgumentType.Switch, "\* Upper"));
// Convert to strongly-typed (if available)
var typedInstruction = TypedFieldInstructionFactory.Create(instruction);
// Reconstruct field code
Console.WriteLine($"Field Code: {instruction.ToString()}");
# Format entire solution
dotnet csharpier format .
# Check formatting
dotnet csharpier check .
Git Hooks
Install git hooks to ensure code quality:
cmake --build build --target install-hooks
This installs a pre-commit hook that:
Runs code formatting
Executes all tests
Prevents commits if tests fail
Testing
The project uses xUnit for testing:
# Run all tests
dotnet test
# Run tests with coverage
dotnet test --collect:"XPlat Code Coverage"
# Run specific test project
dotnet test OpenLanguage.Test/
Performance
OpenLanguage is built with performance as a primary concern:
Native AOT Ready: Full compatibility with .NET Native AOT
Optimized Grammar: LALR YACC-style parser used for SpreadsheetML formula parsing with highly optimized, minimal LEX-style grammar.
Compared against the ABNF grammar specification at each step of implementation.
Compatibility
Multi-framework: Supports both .NET 8.0 and .NET 9.0
Native AOT: Full support for ahead-of-time compilation
TODO
Restructure
Abstract and reuse formula parser's expression lexing and parsing in all
applicable parsers
Remove hand-written C# expression lexer and parser in WordprocessingML
namespace
WordprocessingML
Parsers
Rewrite field instruction parser with yacc-style GPPG parser.
Rewrite field instruction lexer with flex-style GPLEX lexer.
Refactor field instruction classes to use derived classes for strongly-typed instructions
rather than using factories and explicit conversion to strongly typed representation.
Rewrite merge field parser with yacc-style GPPG parser.
Rewrite merge field lexer with flex-style GPLEX lexer.
Test Coverage
Greatly expand field instruction parsing and lexing test coverage. Current
coverage is insufficient for a best-effort proof of efficacy.
Greatly expand mergefield parsing and lexing test coverage. Current
coverage is sparse and does not prove even minimal efficacy.
Misc
Complete exhaustive enumeration of CountryRegion enumerations. The
current implementation is missing all but the most common enumerations.
Evaluation
Implement per-class evaluation of strongly typed field instructions.
Implement evaluation of parsed merge field.
SpreadsheetML
Test coverage is quite comprehensive, as are grammar and parser rule
specifications - there should not be anything left to complete here as far as
implementation of parsing, parsing dependencies, nor AST. However, optimization leaves a bit to be desired, and evaluation is unimplemented.
Optimization
Runtime memory consumption of FormulaParser and AST node classes, as
well as size of generated parser code, jumped by ~10x on adding the
builtin_function_call_head_raw rule. Investigate the cause and resolve.
Many Shift, Reduce, Shift/Reduce, and Reduce/Reduce conflicts are
automatically resolved on code generation of parser. Investigate the cause and
resolve.
Evaluation
Implement evaluation of formula, with a per-AST node class method called
Evaluate, on the abstract ExpressionNode class and overriden by derived
classes.
Implement all builtin SpreadsheetML functions.
Implement cell, sheet, table, and range reference resolution for read
and write of underlying value.
Implement arithmetic expression evaluation.
Implement function reference resolution and call evaluation -
regardless of whether user-defined, _xlpm.-prefixed function references, or
LAMBDA functions.
Bonus: implement a shared SpreadsheetContext to abstract common data
reading and writing operations
Bonus if completed: in SpreadsheetContext, use generic underlying data representation which
is derived from a common Spreadsheet class, allowing any underlying
matrix-like data representation to be manipulated by formulas.
Example Usage
Write a toy formula interpreter when evaluation is implemented.
Bonus: Realtime display and update of spreadsheet cell values in TUI
with matrix display and formula input prompt as well as vim-style selection of
corresponding cells. Simulaneously update underlying OPC package on modifying
values.
Contributing
Fork the repository
Create a feature branch (git checkout -b feature/amazing-feature)
