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<!doctype html>
<html>
<head>
<title>From Python, C++ to Rust</title>
<meta charset="utf-8" />
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name="viewport"
content="user-scalable=no,initial-scale=1,maximum-scale=1,minimum-scale=1,width=device-width"
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<textarea id="source">
layout: true
class: typo, typo-selection
---
count: false
class: nord-dark, middle, center
# 🚀 From Python, C++ to Rust
### A Language Evolution Journey
@luk036 👨💻 · 2026 📅
---
### 📋 Agenda
.pull-left[
**Part 1: Python 🐍 → C++ 🅲**
- Why migrate?
- Auto & Type Deduction
- Range-Based For Loops
- Structured Binding & Tuples
- Uniform Initialization
- If constexpr & CTAD
- Smart Pointers
**Part 2: Modern C++ Performance ⚡**
- std::move & Copy Elision
- Pre-allocation & Reserve
- Sentinel & Invalid State
]
.pull-right[
**Part 3: C++ 🅲 → Rust 🦀**
- Why Rust?
- Ownership & Borrowing
- Error Handling
- Traits vs Concepts
- Performance Comparison
- The Linked List Problem
- The Arena Pattern
**Part 4: The AI Coding Perspective 🤖**
- Build Systems
- Error Messages
- Testing & Tooling
- **The Verdict: When to Use What**
]
---
class: nord-light, middle, center
## 🐍 Part 1: Python → C++
---
### ❓ Why Migrate from Python to C++?
.mermaid[
<pre>
graph LR
subgraph "Python 🐍"
P1["Easy to learn"]
P2["Dynamic typing"]
P3["10-50× slower"]
P4["Great for prototyping"]
end
subgraph "C++ 🅲"
C1["Steeper learning curve"]
C2["Static typing"]
C3["Near-zero overhead"]
C4["Production-ready perf"]
end
P1 -- "but" --> C1
P3 -- "need speed →" --> C3
style P1 fill:#c8e6c9,stroke:#2e7d32,stroke-width:3px
style P3 fill:#ffcdd2,stroke:#c62828,stroke-width:3px
style C3 fill:#e3f2fd,stroke:#1565c0,stroke-width:3px
style C4 fill:#ffe0b2,stroke:#e65100,stroke-width:3px
</pre>
]
> **Strategy**: Python first for exploration, C++ for production deployment
---
### 🧬 Python vs C++: Data Access Types
Python has **one** data access type — C++ has **four**:
C++ gives you fine-grained control: **value**, **reference (&)** , **move (&&)** , **pointer (\*)** .
.font-sm.mb-xs[
.pull-left[
**Python 🐍**
```python
class involution:
def __init__(self, m, o):
self.m = m # always a reference
self.o = o
self.c = m.dot(o)
```
]
.pull-right[
**C++ 🅲**
```cpp
class involution {
L& _m; // reference
P _o; // value
K _c; // value
involution(L &m, P o):
_m{m},
_o{std::move(o)}, // move
_c{m.dot(_o)} {}
};
```
]
]
---
### 🔄 Auto: Python's Dynamic Typing in C++
Python has always been dynamically typed. C++11 introduced `auto` for type deduction:
⚠️ **Watch out**: template expressions in C++ evaluate lazily — `auto` may not do what you expect!
.font-sm.mb-xs[
.pull-left[
**Python 🐍**
```python
def tri(T):
a1, a2, a3 = T
l1 = a2 * a3
l2 = a1 * a3
l3 = a1 * a2
return l1, l2, l3
```
]
.pull-right[
**C++17 🅲**
```cpp
auto tri(const auto &T) {
const auto &[a1, a2, a3] = T;
auto l1 = a2 * a3;
auto l2 = a1 * a3;
auto l3 = a1 * a2;
return std::tuple{
std::move(l1),
std::move(l2),
std::move(l3)};
}
```
]
]
---
### 🔄 Range-Based For Loops
Python's `for` always iterates. C++11+ does too:
⚠️ **Difference**: Python's loop variable leaks; C++'s does not:
```python
for i in range(100): pass
print(i) # prints 99!
```
```cpp
unsigned i;
for (i = 0; i != 100; ++i) {}
std::cout << i; // prints 100
```
.font-sm.mb-xs[
.pull-left[
**Python 🐍**
```python
def coI(l, seq):
for p in seq:
if not l.incident(p):
return False
return True
```
]
.pull-right[
**C++ 🅲**
```cpp
bool coI(L &l, Sequence &seq) {
for (const P &p : seq) {
if (!l.incident(p))
return false;
}
return true;
}
```
]
]
---
### 📦 Structured Binding & Tuples
Python has had tuple unpacking forever. C++17 added structured binding:
CTAD (C++17) deduces template types automatically — `std::tuple{1, 2.5}` not `std::tuple<int, double>{1, 2.5}`.
.font-sm.mb-xs[
.pull-left[
**Python 🐍**
```python
def calc_cc(self):
n = len(self.xc)
rho = 1.0 / (n + 1)
sigma = 2.0 * rho
delta = self.c1
return rho, sigma, delta
# Usage
rho, sigma, delta = obj.calc_cc()
```
]
.pull-right[
**C++17 🅲**
```cpp
auto calc_cc() {
auto n = std::size(this->_xc);
auto rho = 1.0 / (n + 1);
auto sigma = 2.0 * rho;
auto delta = this->_c1;
return std::tuple{rho, sigma, delta};
}
// Usage
auto [rho, sigma, delta] = obj.calc_cc();
```
]
]
---
### 📋 Uniform Initialization
Python dict literal syntax meets C++ STL containers:
C++11 uniform initialization `{}` works with **all** STL containers, arrays, and structs — just like Python dict/set literals.
.font-sm.mb-xs[
.pull-left[
**Python 🐍**
```python
myDict = {5: "foo", 6: "bar"}
print(myDict[5])
```
]
.pull-right[
**C++ 🅲**
```cpp
auto myDict = std::unordered_map{
{5, "foo"sv}, {6, "bar"sv}};
std::cout << myDict[5];
```
]
]
---
### 🔀 If constexpr: Compile-Time Dispatch
C++17's `if constexpr` replaces complex template metaprogramming:
The **dead branch is discarded** at compile time — zero runtime overhead.
.font-sm.mb-xs[
.pull-left[
**Python 🐍**
```python
def ratio_ratio(a, b, c, d):
if isinstance(a, (int, np.int64)):
return Fraction(a,b) / Fraction(c,d)
else:
return (a * d) / (b * c)
```
]
.pull-right[
**C++17 🅲**
```cpp
template <typename K>
auto ratio_ratio(K &a, K &b, K &c, K &d) {
if constexpr (std::is_integral_v<K>) {
return Fraction(a,b) / Fraction(c,d);
} else {
return (a * d) / (b * c);
}
}
```
]
]
---
### 🎯 CTAD: Class Template Argument Deduction
C++17 can deduce template arguments from constructor calls — just like Python:
No more `std::make_pair`, `std::make_tuple` boilerplate!
.font-sm.mb-xs[
.pull-left[
**Python 🐍**
```python
class Interval:
def __init__(self, lower, upper):
self.lower = lower
self.upper = upper
a = Interval(0, 10) # int
b = Interval(1.0, 6.0) # float
```
]
.pull-right[
**C++17 🅲**
```cpp
template <typename T>
struct Interval { T _lower, _upper; };
// Deduction guide (auto-generated in C++20)
Interval(T, T) -> Interval<T>;
auto a = Interval{0, 10}; # int
auto b = Interval{1.0, 6.0}; # double
```
]
]
---
### 🔗 Smart Pointers: Memory Management
Python's GC handles memory. C++ uses RAII + smart pointers:
**Rule of thumb**: `unique_ptr` for exclusive ownership, `shared_ptr` for shared, raw pointer for non-owning access.
.font-sm.mb-xs[
.pull-left[
**Python 🐍**
```python
gainbucket = [
bpqueue(pmax) for _ in range(K)
]
# GC handles cleanup
```
]
.pull-right[
**C++17 🅲**
```cpp
auto gainbucket =
std::vector<std::unique_ptr<bpqueue>>(
K, std::make_unique<bpqueue>(pmax));
// Destroyed when vector goes out of scope
```
]
]
---
### 🏛️ Python-like enumerate() in C++17
.font-sm.mb-xs[
**Python 🐍**
```python
for i, thing in enumerate(listOfThings):
print(f"The {i}th thing is {thing}")
```
**C++17 🅲**
```cpp
std::vector<Thing> things;
for (auto [i, thing] : enumerate(things)) {
fmt::print("The {}th thing is {}", i, thing);
}
```
]
The `enumerate()` adapter returns an iterator yielding `(index, value)` pairs — structured binding makes it feel like Python.
---
### 📊 Python ↔ C++ Library Mapping
.pull-left[
.mermaid[
<pre>
graph LR
subgraph "Python 🐍"
NP["numpy / scipy"]
PT["pytest"]
FM["{fmt} style\nf-strings"]
COR["generator\ncoroutine"]
end
subgraph "C++ 🅲"
XT["xtensor / Eigen"]
CT["Catch2 / doctest"]
FMT["fmt::format()"]
COR2["Boost.Coroutine\n/ cppcoro"]
end
NP --- XT
PT --- CT
FM --- FMT
COR --- COR2
style NP fill:#c8e6c9,stroke:#2e7d32,stroke-width:3px
style XT fill:#e3f2fd,stroke:#1565c0,stroke-width:3px
style PT fill:#c8e6c9,stroke:#2e7d32,stroke-width:3px
style CT fill:#e3f2fd,stroke:#1565c0,stroke-width:3px
</pre>
]
]
.pull-right[
| Python | C++ Equivalent |
|:-------|:---------------|
| `numpy.dot(a, b)` | `xt::linalg::dot(a, b)` |
| `np.linspace(1,8,50)` | `xt::linspace<double>(1,8,50)` |
| `pytest.approx` | `Catch2::Approx` |
| `f"{x:.3f}"` | `fmt::format("{:.3f}", x)` |
]
---
class: nord-light, middle, center
## ⚡ Part 2: Modern C++ Performance
---
### 🏎️ std::move: Avoid Expensive Copies
**Cost**: `std::move` is essentially free — just a pointer swap. ❌ No deep copy.
.font-sm.mb-xs[
.pull-left[
**Before (copies)**
```cpp
auto createBigData(size_t n) {
auto BigData = std::vector<int>(n);
// ...
if (beta > tau) {
return {1, BigData}; // COPY!
}
return {0, BigData}; // COPY!
}
```
]
.pull-right[
**After (moves) ⚡**
```cpp
auto createBigData(size_t n) {
auto BigData = std::vector<int>(n);
// ...
if (beta > tau) {
return {1, std::move(BigData)};
}
return {0, std::move(BigData)};
}
```
]
]
---
### 📦 Pre-allocation: Reserve Memory
**Impact**: Up to **79% faster** for large vectors — no reallocation, no moves, no cache misses.
.font-sm.mb-xs[
.pull-left[
**Before (reallocates)**
```cpp
auto nets =
std::vector<node_t>{};
for (auto net : H.nets) {
if (!S.contains(net)) {
nets.push_back(net);
// may reallocate!
}
}
```
]
.pull-right[
**After (pre-allocated) ⚡**
```cpp
auto nets =
std::vector<node_t>{};
nets.reserve(
H.nets.size() - S.size());
for (auto net : H.nets) {
if (!S.contains(net)) {
nets.push_back(net);
// no reallocation
}
}
```
]
]
---
### 🎯 Sentinel Pattern: Eliminate Boundary Checks
**Trick**: Place a sentinel node at index 0 that's always non-empty. The loop naturally stops.
.mermaid[
<pre>
graph TD
subgraph "With Sentinel"
B2["bucket[0..100]\nsentinel at [0]"] --> C2["no boundary check"]
C2 --> D2["straight-line\nfast path"]
end
subgraph "Traditional"
B1["bucket[0..99]"] --> C1["check max >= 0\nevery iteration"]
C1 --> D1["branch mispredicts\nslow path"]
end
style D1 fill:#ffcdd2,stroke:#c62828,stroke-width:3px
style D2 fill:#c8e6c9,stroke:#2e7d32,stroke-width:3px
</pre>
]
.font-sm.mb-xs[
.pull-left[
**Before (boundary check)**
```cpp
while (max >= 0 // check!
&& bucket[max].is_empty()) {
max -= 1;
}
```
]
.pull-right[
**After (sentinel) ⚡**
```cpp
while (bucket[max].is_empty()) {
max -= 1; // no check needed!
}
```
]
]
---
### 🔄 Utilize Invalid State
Don't allocate a separate `visited` array — reuse existing state:
Saved: one `vector<bool>` allocation (and `vector<bool>` is notoriously slow).
.font-sm.mb-xs[
.pull-left[
**Before (extra memory)**
```cpp
std::vector<bool> visited(N, false);
while (!Q.empty()) {
auto v = Q.front();
Q.pop_front();
if (visited[v]) continue;
// ...
visited[v] = true;
}
```
]
.pull-right[
**After (no allocation) ⚡**
```cpp
std::fill(part.begin(), part.end(), K);
while (!Q.empty()) {
auto v = Q.front();
Q.pop_front();
if (part[v] < K) continue;
part[v] = extern_module_ss[v];
// Saved a vector `visited`
```
]
]
---
class: nord-light, middle, center
## 🦀 Part 3: C++ → Rust
---
### ❓ Why Rust?
.mermaid[
<pre>
graph TD
subgraph "C++ 🅲"
C1["Manual memory\nmanagement"]
C2["Undefined behavior\n(use-after-free, etc.)"]
C3["No thread safety\nguarantees"]
C4["Template error\nfirehose"]
end
subgraph "Rust 🦀"
R1["Ownership + Borrow\nChecked at compile time"]
R2["No undefined behavior\nin safe code"]
R3["Fearless concurrency\nSend + Sync traits"]
R4["Clear, actionable\nerror messages"]
end
C1 --> R1
C2 --> R2
C3 --> R3
C4 --> R4
style C1 fill:#ffcdd2,stroke:#c62828,stroke-width:3px
style C2 fill:#ffcdd2,stroke:#c62828,stroke-width:3px
style C3 fill:#ffe0b2,stroke:#e65100,stroke-width:3px
style C4 fill:#ffe0b2,stroke:#e65100,stroke-width:3px
style R1 fill:#c8e6c9,stroke:#2e7d32,stroke-width:3px
style R2 fill:#c8e6c9,stroke:#2e7d32,stroke-width:3px
style R3 fill:#e3f2fd,stroke:#1565c0,stroke-width:3px
style R4 fill:#e3f2fd,stroke:#1565c0,stroke-width:3px
</pre>
]
> **The promise**: Memory safety without garbage collection. Zero-cost abstractions.
---
### 🏛️ Type Systems: Traits vs Templates
.font-sm[
.pull-left[
**Rust** — Trait-based generics with explicit contracts:
```rust
pub trait Overlap<T> {
fn overlaps(&self, other: &T) -> bool;
}
pub trait MinDist<T> {
fn min_dist_with(&self, other: &T) -> u32;
}
// Compose via trait bounds
impl<T1, T2, U1, U2> Overlap<Point<U1, U2>>
for Point<T1, T2>
where T1: Overlap<U1>, T2: Overlap<U2>
{ /* ... */ }
```
]
.pull-right[
**C++20** — Concepts with `requires` clauses:
```cpp
template <typename U1, typename U2>
constexpr auto overlap(const U1& lhs, const U2& rhs)
-> bool {
if constexpr (requires { lhs.overlaps(rhs); }) {
return lhs.overlaps(rhs);
} else { return lhs == rhs; }
}
```
]
]
---
### 🏛️ The Composability Advantage
Rust traits compose naturally — `Point` delegates to its components:
```rust
impl<T1, T2, U1, U2> Overlap<Point<U1, U2>>
for Point<T1, T2>
where T1: Overlap<U1>, T2: Overlap<U2>
{
fn overlaps(&self, other: &Point<U1, U2>) -> bool {
self.xcoord.overlaps(&other.xcoord)
&& self.ycoord.overlaps(&other.ycoord)
}
}
```
**Key insight**: `Point<Interval<i32>, Interval<i32>>` automatically gets rectangle overlap from `Interval`'s implementation. **Zero boilerplate, zero cost** — fully monomorphized.
---
### 🎯 Error Handling: Algebraic vs Ad-Hoc
**Rust** — Enum with pattern matching, propagate via `?`:
```rust
pub enum GeomError {
InvalidPolygon(String),
SelfIntersectingPolygon,
DegeneratePolygon { vertex_count: usize },
NumericalError(String),
}
pub type GeomResult<T> = Result<T, GeomError>;
fn process(poly: &Polygon) -> GeomResult<f64> {
let area = poly.area()?; // propagate error
Ok(area * 2.0)
}
```
**C++** — Mixed approach (assertions, exceptions):
```cpp
assert(!this->is_locked()); // runtime crash if violated
// No standardized error type
```
**Impact**: Rust's approach catches geometry violations at **compile-time** via the type system. C++ relies on runtime checks.
---
### 🔐 Ownership & Borrowing
The single biggest mental shift from C++ to Rust:
.mermaid[
<pre>
graph TD
subgraph "C++ 🅲"
CP["Pointer to T"] --> CD["May be:\n- Valid ✅\n- Null ❌\n- Dangling 💀"]
end
subgraph "Rust 🦀"
RR["&T (shared ref)"] --> RS["Multiple readers\nNo writers"]
RW["&mut T (unique ref)"] --> RM["Single writer\nNo readers"]
RO["Box<T> (owned)"] --> RM2["Move semantics\nRAII drop"]
end
style CD fill:#ffcdd2,stroke:#c62828,stroke-width:3px
style RS fill:#c8e6c9,stroke:#2e7d32,stroke-width:3px
style RM fill:#e3f2fd,stroke:#1565c0,stroke-width:3px
style RM2 fill:#ffe0b2,stroke:#e65100,stroke-width:3px
</pre>
]
> **Rust rule**: Either **one mutable reference** XOR **any number of immutable references**. Enforced at compile time.
---
### 📊 Performance: Static Dispatch Costs Zero
.font-sm[
| Mechanism | Time | vs Free Function |
|:----------|:----:|:----------------:|
| **Free function** | 1.54 ns | **1.00x** |
| **Static dispatch** (monomorphized) | 1.61 ns | **1.04x** (noise) |
| **Dynamic dispatch** (vtable) | 2.90 ns | **1.88x** |
]
**Error handling cost on success path** — zero:
.font-sm[
| Pattern | Time | vs `assert!` |
|:--------|:----:|:------------:|
| `assert!(b != 0)` | 4.36 ns | **1.00x** |
| `Result::Ok(x)` + `.unwrap()` | 4.36 ns | **1.00x** |
| `Option::Some(x)` + `.unwrap()` | 4.36 ns | **1.00x** |
]
Both `Result` and `Option` compile to **identical machine code** as unchecked operations.
---
### ⛓️ The Linked Data Structure Problem
Self-referential structs are Rust's **Achilles' heel**:
```rust
pub struct Dllink<T> {
pub next: *mut Dllink<T>, // raw pointer
pub prev: *mut Dllink<T>, // raw pointer
pub data: T,
_marker: PhantomData<*mut T>, // opts out of Send/Sync
}
```
```cpp
template <typename T> class Dllink {
public:
Dllink* next{this}; // self-referencing sentinel!
Dllink* prev{this};
T data{};
};
```
**Key difference**: C++ uses a self-pointer sentinel (`next == this` means locked). Rust needs raw pointers and `unsafe` — borrow checker cannot verify cyclic graphs.
---
### ⛓️ The Arena: Safe Intrusive Data Structures
.pull-left[
Both languages solve this the same way — store nodes in a contiguous `Vec`/`vector`:
**Critical invariant**: `with_capacity(3 * num_nodes)` prevents reallocation that would invalidate all pointers.
**Index arena alternative** — zero `unsafe`, move-safe, but **36% slower** traversal:
]
.pull-right[
| Method | Time | vs Baseline |
|:-------|:----:|:-----------:|
| **Raw pointer** (current) | **3.66 µs** | **1.00x** |
| **Arena index** (alternative) | **4.96 µs** | **1.36x** |
]
.font-sm.mb-xs[
.pull-left[
**Rust 🦀**
```rust
pub struct RDllist {
pub cycle:
Vec<Dllink<usize>>,
}
```
]
.pull-right[
**C++ 🅲**
```cpp
class RDllist {
public:
std::vector<Dllink<size_t>>
cycle;
};
```
]
]
---
### ⛓️ Design Spectrum for EDA Data Structures
```
Safer ←─────────────────────────────────→ Faster
Index Arena Raw Ptr Arena Raw Ptr (heap)
(usize indices) (Vec + pointers) (Box + Rc + RefCell)
| | |
Zero unsafe unsafe needed Heavy overhead
Move-safe Realloc fragile Cache-unfriendly
36% slower Baseline perf "Linked list in Rust"
```
.mermaid[
<pre>
graph LR
A["Index Arena\n🛡️ Safest"] --> B["Raw Ptr Arena\n⚡ Best for EDA"]
B --> C["Box+Rc+RefCell\n🐢 Avoid for hot paths"]
A -- "polygon cut\nalgorithms need\nthis speed" --> B
C -- "but this is what\nbeginners reach for" --> B
style A fill:#c8e6c9,stroke:#2e7d32,stroke-width:3px
style B fill:#e3f2fd,stroke:#1565c0,stroke-width:3px
style C fill:#ffcdd2,stroke:#c62828,stroke-width:3px
</pre>
]
---
### 📊 Rust vs C++: Geometry Kernel Benchmark
Rust benchmarks (optimized release, 20-core x86-64):
.font-sm.mb-xs[
| Operation | Time | Ops/sec |
|:----------|:----:|:-------:|
| Point creation | **1.74 ns** | 575M |