Ross' Engineering Toolbox

• TODO: Table of contents here

Theory

Programming Lanuages

Compilers

• A compiler is a program that translates one programming lanuage into another programming language, usually, a higher level programming language is translated by a compiler to a lower level programming language, such as assembly or machine code
• When building a new programming language, the initial compiler for the language must be written using a different programming language. This is called bootstrapping a compiler Ex. the first compiler for Go was written in C. Once Go was stable, the Go compiler code that was written in C was rewritten in Go (link).

Interpreted vs. Compiled

• Languages are often said to be either interpreted or compiled, but this is not strictly true. An implementation of a language can either be interpreted or compiled.
• Interpreted implementations of a language will move line by line through the language and transform it into some intermediary, platform agnostic bytecode / p-code (portable code). This bytecode can then either be run on a virtual machine (portable code machine (p-code machine) that is specifically designed to execute the bytecode, OR compiled with Just-In-Time (JIT) compilation into machine code and run directly on the host system.
  • Note that bytecode is distinct from an instruction set architecture (ISA)

Client Design

Filtering

When designing a data driven client, you may want to filter data. Filtering is easiest to think about in terms of sets. Selecting multiple filter fields can either result in the UNION (OR) of two underlying sets of data, or the INTERSECTION (AND).

• Ex. - Selecting 'Group 1' and 'Football' can either return all users that are in Group 1 AND play Football, or all users that are in Group 1 OR play Football.

Databases

Postgres

Quick Links

These are some quick links to postgres documentation that I find myself using often.

• Roles and Privileges
• SELECT

New Install

Upon installing a new version of postgres the first thing you will need to to is create a role and a database for that role for whatever your username on your local machine is. You'll also probably want to make yourself a superuser. You may additionally want to set a password for your role for use in database URLS such as postgres://rossgrat:password@localhost:5432/test-database. All of those things are taken care of in the below sequence of commands.

$ psql postgres
# CREATE ROLE rossgrat;
# CREATE DATABASE rossgrat;
# ALTER ROLE rossgrat WITH SUPERUSER;
# ALTER ROLE rossgrat WITH PASSWORD 'password';

CLI

• You can exeute SQL code directly from the command line using psql -c 'SELECT ...'
• Create a dump of a database to your local machine using pg_dump <database_url> > out.sql
• Restore a local dump to a database using psql <database_url> < out.sql

SQL

• You can make a copy of a database directly on a postgres server instance using:

      CREATE DATABASE new_database WITH TEMPLATE old_database;

• You can remove all connections except your own from a database using:

  SELECT pg_terminate_backend(pg_stat_activity.pid)
  FROM pg_stat_activity
  WHERE pg_stat_activity.datname=<database_name>
  AND pid != pg_backend_pid()

Programming Languages

General

• Many languages have getters and setters that allow class variables to execute functions when they are updated. This can be useful for dynamically changing variables or updating. Examples in Typescript and Swift are below.

  // Typescript
  class Person {
      firstName: string
      lastName: string
      get fullName() {
          return this.firstName + ' ' + this.lastName
      }
      set fullName(fullName: string) {
          let strs = fullName.split(' ')
          if (strs.length > 0) {
              this.firstName = strs[0]
          }
          if (strs.length > 1) {
              this.lastName = strs[1]
          }
      }
  }

  // Swift
  class Person {
      var firstName: String
      var lastName: String
      var fullName: String {
          get {
              return this.firstName + " " + this.lastName
          }
          set {
              ...
          }
      }
  }

  Go

  • Go is organized by modules, here are some helpful links for organizing Go projects
    • Creating and using modules
    • Calling a module from another module
    • Module import paths
    • Ideas for a Go project structure

Cloud Hosting

AWS

S3 Buckets

• When creating an S3 bucket, a bucket policy, found under the permissions tab for the bucket, is necessary for defining how the objects in the bucket are accessed. Trying to access data in a bucket without this policy will result in errors, most often 403 "AccessDenied" errors

IDEs

Visual Studio Code

Linters

It is often useful to have a Linter to help you pick out bugs in your IDE, especially for dynamically typed languages. Some extensions for VS Code, like the Go extension, contain everything you need to develop the language, including a Linter. others do not. Here are some visual code extensions for Linters:

• Python (PyLint)
• Javascript/Typescript (ESLint)
  • Great article on using ESLint with VS Code