feat(phase-4): Type-Safe Arithmetic & Comparisons #118
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Improve float division by zero handling to approximate Lua 5.3 behavior. Instead of raising errors, float division by zero now returns very large numbers as approximations of infinity. Changes: - Update safe_divide to handle division by zero cases - Positive / 0 returns 1.0e308 (approximating +inf) - Negative / 0 returns -1.0e308 (approximating -inf) - 0 / 0 returns 0.0 (approximating NaN) - Update tests to reflect the approximation approach - Document limitation vs true Lua 5.3 infinity/NaN support Note: Elixir/Erlang's strict arithmetic makes true IEEE 754 infinity/NaN difficult to create. This is a known limitation. Arithmetic type checking (Phase 4A) was already complete: - All arithmetic operations use safe_* helpers with type checking - TypeError raised for non-numeric operands - String-to-number coercion follows Lua semantics Comparison safety (Phase 4C) was already complete: - == and != work on any types - <, <=, >, >= work on numbers or strings (same type) - TypeError raised for incompatible type comparisons - Lexicographic string comparison All 1,011 tests passing. Implements Phase 4 from plan.md
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I'm not sure that we want to do this, I think we should potentially diverge from Lua 5.3 in this case |
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Type-Safe Arithmetic & Comparisons
Goal
Proper Lua 5.3 arithmetic semantics with clear error messages.
Implementation
Float Division by Zero: Updated to approximate Lua 5.3 behavior:
positive / 0returns1.0e308(approximating +inf)negative / 0returns-1.0e308(approximating -inf)0 / 0returns0.0(approximating NaN)Note: True IEEE 754 infinity/NaN are difficult to create in Elixir/Erlang due to strict arithmetic checks. This is a documented limitation.
Arithmetic Type Checking (already complete):
safe_*helpers with type checkingTypeErrorraised for non-numeric operands with clear messagesComparison Safety (already complete):
==and~=work on any types (return false for different types)<,<=,>,>=only work on numbers or strings (same type)TypeErrorraised for incompatible type comparisonsChanges
lib/lua/vm/executor.ex- Updatedsafe_divideto handle division by zerotest/lua/vm/arithmetic_test.exs- Updated division by zero testsVerification
mix formatcompletedmix compile --warnings-as-errorspassesmix test --exclude pendingpasses (1,011 tests)