Add Result type for consistent error propagation #59

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opened 2026-02-07 17:11:02 +00:00 by navicore · 0 comments

navicore commented

2026-02-07 17:11:02 +00:00

(Migrated from github.com)

Summary

Adopt a consistent Result type (Ok/Err) for error propagation throughout the evaluator, inspired by the seq-lisp-2 experiment.

Motivation

Currently seq-lisp uses a mix of approaches for error handling:

#f returns
String error messages
Crashes/panics

seq-lisp-2 demonstrated a clean Result union type (Ok/Err) threaded through the entire evaluator, making error propagation explicit and consistent. Every operation that can fail returns a Result.

Scope

Define Result union type in src/types.seq or equivalent
Thread Result through evaluator dispatch in src/eval.seq
Update all builtin operations to return Result
Ensure try/catch mechanism works with the new type
Maintain backward compatibility with existing Lisp-level error handling

Notes

This is the most invasive change of the seq-lisp-2 back-ports — it touches nearly every function in the Seq-level evaluator. Should be planned carefully and possibly done incrementally.

Inspired by seq-lisp-2/src/types.seq and seq-lisp-2/src/eval.seq.

## Summary Adopt a consistent `Result` type (`Ok`/`Err`) for error propagation throughout the evaluator, inspired by the seq-lisp-2 experiment. ## Motivation Currently seq-lisp uses a mix of approaches for error handling: - `#f` returns - String error messages - Crashes/panics seq-lisp-2 demonstrated a clean `Result` union type (`Ok`/`Err`) threaded through the entire evaluator, making error propagation explicit and consistent. Every operation that can fail returns a `Result`. ## Scope - Define `Result` union type in `src/types.seq` or equivalent - Thread `Result` through evaluator dispatch in `src/eval.seq` - Update all builtin operations to return `Result` - Ensure `try`/catch mechanism works with the new type - Maintain backward compatibility with existing Lisp-level error handling ## Notes This is the most invasive change of the seq-lisp-2 back-ports — it touches nearly every function in the Seq-level evaluator. Should be planned carefully and possibly done incrementally. Inspired by `seq-lisp-2/src/types.seq` and `seq-lisp-2/src/eval.seq`.