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I don't know Ada; care to explain why its definition of safety is broader than Rust? I agree Rust's safety is very clearly (and maybe narrowly) defined, but it

I don't know Ada; care to explain why its definition of safety is broader than Rust? I agree Rust's safety is very clearly (and maybe narrowly) defined, but it doesn't mean there isn't focus on general correctness - there is. The need to define safety precisely arises because it's part of the language (`unsafe`).

naasking 1y ago
As the OP mentioned, restricted number ranges: with Ada.Text_IO; use Ada.Text_IO; procedure Restricted_Number_Demo is -- Define a restricted subtype of Integer subtype Small_Positive is Integer range 1 .. 100; -- Define a restricted subtype of Float subtype Probability is Float range 0.0 .. 1.0; -- Variables of these restricted types X : Small_Positive := 42; P : Probability := 0.75; begin Put_Line("X = " & Integer'Image(X)); Put_Line("P = " & Float'Image(P)); -- Uncommenting the following line would raise a Constraint_Error at runtime -- X := 200; end Restricted_Number_Demo;
yukeabu 1y ago
Rust’s built-in notion of safety is intentionally focused on memory + data-race properties at compile time. logic, timing, and determinism are left to libraries and design. Ada (with SPARK & Ravenscar) treats contracts, concurrency discipline, and timing analysis as first-class language/profile concerns hence a broader safety envelope. You may choose to think from safety guarantee hierarchy perspective like (Bottom = foundation... Top = highest assurance) Layer 6: FORMAL PROOFS (functional correctness, no RT errors) Ada/SPARK: built-in (GNATprove) Rust: external tools (Kani, Prusti, Verus) Layer 5: TIMING / REAL-TIME ANALYSIS (WCET, priority bounds) Ada: Ravenscar profile + scheduling analysis Rust: frameworks (RTIC, Embassy) Layer 4: CONCURRENCY DETERMINISM (predictable schedules) Ada: protected objects + task priorities Rust: data-race freedom; determinism via design Layer 3: LOGICAL CONTRACTS & INVARIANTS (pre/post, ranges) Ada: Pre/Post aspects, type predicates (built-in) Rust: type states, assertions, external DbC tools Layer 2: TYPE SAFETY (prevent invalid states) Ada: range subtypes, discriminants Rust: newtypes, enums, const generics Layer 1: MEMORY SAFETY & DATA-RACE FREEDOM Ada: runtime checks; SPARK proves statically Rust: compile-time via ownership + Send/Sync

naasking 1y ago

As the OP mentioned, restricted number ranges: with Ada.Text_IO; use Ada.Text_IO; procedure Restricted_Number_Demo is -- Define a restricted subtype of Integer subtype Small_Positive is Integer range 1 .. 100; -- Define a restricted subtype of Float subtype Probability is Float range 0.0 .. 1.0; -- Variables of these restricted types X : Small_Positive := 42; P : Probability := 0.75; begin Put_Line("X = " & Integer'Image(X)); Put_Line("P = " & Float'Image(P)); -- Uncommenting the following line would raise a Constraint_Error at runtime -- X := 200; end Restricted_Number_Demo;

yukeabu 1y ago

Rust’s built-in notion of safety is intentionally focused on memory + data-race properties at compile time. logic, timing, and determinism are left to libraries and design. Ada (with SPARK & Ravenscar) treats contracts, concurrency discipline, and timing analysis as first-class language/profile concerns hence a broader safety envelope. You may choose to think from safety guarantee hierarchy perspective like (Bottom = foundation... Top = highest assurance) Layer 6: FORMAL PROOFS (functional correctness, no RT errors) Ada/SPARK: built-in (GNATprove) Rust: external tools (Kani, Prusti, Verus) Layer 5: TIMING / REAL-TIME ANALYSIS (WCET, priority bounds) Ada: Ravenscar profile + scheduling analysis Rust: frameworks (RTIC, Embassy) Layer 4: CONCURRENCY DETERMINISM (predictable schedules) Ada: protected objects + task priorities Rust: data-race freedom; determinism via design Layer 3: LOGICAL CONTRACTS & INVARIANTS (pre/post, ranges) Ada: Pre/Post aspects, type predicates (built-in) Rust: type states, assertions, external DbC tools Layer 2: TYPE SAFETY (prevent invalid states) Ada: range subtypes, discriminants Rust: newtypes, enums, const generics Layer 1: MEMORY SAFETY & DATA-RACE FREEDOM Ada: runtime checks; SPARK proves statically Rust: compile-time via ownership + Send/Sync