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Bending the curve

A personal tutor at your fingertips

Esteban Küber

he / him

@ekuber

@estebank

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Bending the curve

A personal tutor at your fingertips

Esteban Küber

he / him

@ekuber

@estebank

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Bending the curve

A personal tutor at your fingertips

Esteban Küber

he / him

@ekuber

@estebank

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Bending the curve

So you want to write a programming language

A personal tutor at your fingertips

that people use

Esteban Küber

he / him

@ekuber

@estebank

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Map
Explore
Travel guide/neighbour/friend

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Map
Explore
Travel guide/neighbour/friend

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Explore

Mental map

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[pizza place pic next to red house]

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Map
Explore
Travel guide/neighbour/friend

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[fancy pizza shop]

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[city bus pic in the background with travel card in the foreground]

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[intentionally left blank]

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[pizza place pic next to red house]

[CODE]

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Why design a

programming language?

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Why design a

programming language?

Objectives

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[copyrighted character missing]

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Objectives

Runtime and design flexibility

Restrict performance

Final execution speed

Slower compilation speed
Restrict dynamism

Compilation speed

Restrict features and ergonomics

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[crate and code showing file split]

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Don’t try to read this 🙃

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Objectives

Runtime and design flexibility

Restrict performance

Final execution speed

Slower compilation speed
Restrict dynamism

Compilation speed

Restrict features and ergonomics

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Objectives

Runtime and design flexibility

Restrict performance

Final execution speed

Slower compilation speed
Restrict dynamism

Compilation speed

Restrict features and ergonomics

Learnability

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Language design

Syntax / Grammar
Semantics
Features

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Type[ParamA, ParamB]

Type<ParamA, ParamB>

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Type[ParamA, ParamB]

Type<ParamA, ParamB>

Type::<ParamA, ParamB>

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null

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Borrow checker
Non-representability of null
Immutability by default
etc

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Steve Klabnik

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Don’t try to read this 🙃

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Arc<RefCell<T>>

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TL;DR:

“Borrow” liberally from other languages

Make sure it fits with the rest of your language

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Many things affect how easy to learn a language

Libraries
Documentation
Tooling
Platform support
Community

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💸

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Many things affect how easy to learn a language

Libraries
Documentation
Tooling
Platform support
Community

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Many things affect how easy to learn a language

Libraries
Documentation
Tooling

Code formatters
Linters
Debuggers
Package managers
IDEs

Platform support
Community

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“Introducing a new tool to aid your learning”

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“Introducing a new tool to aid your learning”

Tuto.rs

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“Introducing a new tool to aid your learning”

Tuto.rs

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“Introducing a new tool to aid your learning”

Optional
Undiscoverable
“Second child” syndrome

Tuto.rs

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[citation needed]

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Types of errors

Parse errors

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[Extra > in path]

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Type ascription

Nightly only
Annotates any expression with a type
<expr>: <type>

Looks like let binding with types, function argument bindings and struct field bindings

Extremely easy to make a typo that looks like it

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Types of errors

Parse errors
“Negative space” boundary errors

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[Cartesian space IN/OUT b&w]

[Cartesian space IN/OUT b&shades of grey]

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the tutor needs context,�knowledge of the tutee

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the tutor needs context,�knowledge of the tutee

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the tutor needs context,�knowledge of the tutee

and it has it

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[contextless error that we already handle]

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[“oracle” diagnostics paper front or conclussions page]

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&str vs String

String


h	e	l	l	o	,		w	o	r	l	d


h	e	l	l	o	,		w	o	r	l	d

len	ptr
12


h	e	l	l	o	,		w	o	r	l	d

capacity	len	ptr
12	12

&str

str

this is in the heap!

std::string::

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&str vs String


h	e	l	l	o	,		w	o	r	l	d

this is in the heap!

String

capacity	len	ptr
12	12

std::string::

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&str vs String

len	ptr
2


h	e	l	l	o	,		w	o	r	l	d

&str

this is in the heap!

len	ptr
5

&str

len	ptr
12

String

capacity	len	ptr
12	12

std::string::

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&str vs String


h	e	l	l	o	,		w	o	r	l	d


h	e	l	l	o	,		w	o	r	l	d

len	ptr
12


h	e	l	l	o	,		w	o	r	l	d

&str

str

this is in the heap!

String

capacity	len	ptr
12	12

std::string::

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&str vs String


h	e	l	l	o	,		w	o	r	l	d


h	e	l	l	o	,		w	o	r	l	d

len	ptr
12


h	e	l	l	o	,		w	o	r	l	d

&str

str

this is in the heap!

Vec<u8>

Vec<char>

Utf-8�Utf-16

utf-32

&String

impl Deref<Target=&str> for &String

OsString

Path�\0

Sized

?Sized

‘a

String

capacity	len	ptr
12	12

std::string::

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&str vs String


h	e	l	l	o	,		w	o	r	l	d


h	e	l	l	o	,		w	o	r	l	d

len	ptr
12


h	e	l	l	o	,		w	o	r	l	d

&str

str

this is in the heap!

If you’re coming from Java,

this is a StringBuffer

If you’re coming from C,

this is string literal in your binary

If you’re coming from C++,

this is string_view

String

capacity	len	ptr
12	12

std::string::

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Don’t try to read this 🙃

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Don’t try to read this 🙃

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Don’t try to read this 🙃

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[XML vs JSON: simplicity of the language has a benefit]

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To summarize

To make your language easy to use, steal from others
There are things beyond “the language” that makes people learn it and stick around
Your compiler can and should do more
Demand better from your tools