Meta
Programming
Presented by
Arnaud Buchholz
Presentation made with
Reveal.js
Agenda
### The 5 **W** ||| |---|---| |**Who**|Me| |**When**|Over the last 5 months| |**Where**|The [`psbots`](https://github.com/ArnaudBuchholz/psbots) project| |**What**|**Generate** TypeScript and <br/>**Manipulate** *transpiled* JavaScript| |**Why**|**Efficiency**, **Analysis** and **Optimization**| --- #### A **Brief** Introduction To `psbots` * PostScript **interpreter** * Developed in **TypeScript** *(no dependencies)* * Focused on **maintainability** and **performance** * Heavily **tested** (example: [`repeat`](https://github.com/ArnaudBuchholz/psbots/blob/main/engine/src/core/operators/flow/repeat.ts#L45)) --- #### `psbots` **demo** * wi : `debug 4 "abc" repeat` * cli : `100 perf` --- ### **Meta**programming According to [wiki](https://en.wikipedia.org/wiki/Metaprogramming) > Metaprogramming is a computer programming **technique** in which computer programs have the ability to treat other programs as their **data**. --- #### Examples ||| |---|---| |**Compilers**|C, Java, TypeScript...| |**Linters**|eslint, dpdm...| |**Bundlers**|webpack, vite...| |**Security Scanners**|BlackDuck, Renovate...| --- ### Beginner : **Generation** *When sources are same / same but different...* --- #### Example : Source **Automation** Source files are **generated** using a [script](https://github.com/ArnaudBuchholz/psbots/blob/main/engine/tools/makeSources.mjs) : * Barrel imports (i.e. [`index.ts`](https://github.com/ArnaudBuchholz/psbots/blob/main/engine/src/core/operators/index.ts)) * Exceptions files (i.e. [`dictStackUnderflow.ts`](https://github.com/ArnaudBuchholz/psbots/blob/main/engine/src/core/operators/exceptions/dictStackUnderflow.ts)) * from [`system-exceptions.json`](https://github.com/ArnaudBuchholz/psbots/blob/main/engine/tools/system-exceptions.json) --- #### PROs / CONs * 👍 **Automated** during the build * 👍 One **source** of truth * 👍 Easier to **maintain** * 👎 Risk of **overwriting** *(warning added)* * 💡 Leverage the **linter** --- ### **A**bstract **S**yntax **T**ree According to [wiki](https://en.wikipedia.org/wiki/Abstract_syntax_tree) > An abstract syntax tree (AST) is a **data structure** used in computer science to represent the structure of a **program**. --- #### AST **Explorer** * [Hello World!](https://astexplorer.net/#/gist/a34712863759bfe13d9df5be1e9fa775/6af937770e063e15f5f6e255817adbce901dd64b) * `"Hello " + "World!"` * `const msg = "Hello World!"` * Different **parsers**, *almost* the same result * `babel` * `esprima` * `uglify-js` --- ### Intermediate : **Analysis** *When the codebase **grows** significantly,* *how do you **get insights** from the sources ?* --- #### Example : **Dependency** Analysis Documentation of [sources' dependencies](https://github.com/ArnaudBuchholz/psbots/blob/main/docs/engine/sources.md) : * Source [`engineSources.mjs`](https://github.com/ArnaudBuchholz/psbots/blob/main/docs/build/engineSources.mjs) * **Parsing** using [`@babel/parser`](https://www.npmjs.com/package/@babel/parser) and [`@babel/traverse`](https://www.npmjs.com/package/@babel/traverse) * **Rendering** using [`mermaid`](https://mermaid.js.org/) --- #### PROs / CONs * 👍 Custom **insight** on the codebase * 👎 Must handle **all** syntaxes *(for instance: function definition and call)* * 👎 Very **bad** documentation of `@babel/traverse` * 💡 Use **LLMs** to figure out API --- ### Advanced : **Optimization** *Code is **linted** and **maintainable**,* *but is it **fast** ?* --- #### How To **Measure** JavaScript Performances ? * Understand the **host** * Understand the **platform** * Collect and eliminate **aberrant** values [test](https://github.com/ArnaudBuchholz/psbots/blob/main/engine/tools/test.mjs) and [TimeBucket](https://github.com/ArnaudBuchholz/psbots/blob/main/engine/tools/TimeBucket.mjs) --- #### Example : **Removing** Assertions (1/2) ```typescript function assert<T>(result: Result<T>): asserts result is { success: true; value: T }; function assert(condition: boolean, message?: string, cause?: unknown): asserts condition; ``` The `assert` function is used to : * **Validate** that a function call succeeded<br/>(use of [`Result`](https://github.com/ArnaudBuchholz/psbots/blob/main/engine/src/api/Result.ts) type) * **Assess** a condition * [Examples](https://github.com/ArnaudBuchholz/psbots/blob/main/engine/src/core/operators/stacks/operand/roll.ts#L33) --- #### Example : **Removing** Assertions (2/2) * The `assert` function **throws** exceptions which **fail** the engine * **On build**, the `assert` function is **useless** --- #### Example : **Inlining** `toValue` Functions * The engine **manipulates** values<br/>which structure follows a **strict** [definition](https://github.com/ArnaudBuchholz/psbots/blob/main/engine/src/api/values/Value.ts) * To avoid error while using **literal** objects,<br/>**helper** functions do the **conversion** * **On build**, the functions are **inlined** --- #### Demo * Removing `assert` * `src/api/parser.ts` * Inlining `toIntegerValue` * `src/core/operators/stacks/operand/roll.ts` --- #### Example : All The **Ideas** * [Documented ideas](https://github.com/ArnaudBuchholz/psbots/blob/main/docs/engine/Optimizations.md) * And others : * `for(of)` ➟ `for(index;;)` * `if/else` ➟ `switch` --- #### PROs / CONs * 👍 Keep the code **readable** and **maintainable** * 👍 Prioritize functionality **over** optimization * 👎 Complex and **expensive** to implement * 👎 Not **all** ideas are good --- ### Key **Take-Aways** * Metaprogramming is a **powerful tool** * **Steep** learning curve but **rewarding**
