How to write a programming language – Part 1, The Lexer

I wrote a little programming language, Cell which is supposed to be simple enough to help explain how a programming language works.

Here’s the explanation of the lexer, which is the first part of a compiler or interpreter.

Slides: How to write a programming language – Part 1, The Lexer

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Gracefully shutting down Firefox, to avoid the crash/session dialog

I normally have several Firefox profiles open, and when I log out without closing the Firefox windows I get the “session restore” dialog on my next login.

This is because of Bug 336193 which says that Firefox should shut down gracefully when it receives a SIGTERM signal, which is what happens when I log out (in Ubuntu MATE anyway). At the moment, it shuts down ungracefully, meaning it is treated as if Firefox crashed when it restarts.

So, instead of my normal shutdown button, I have one that launches a script that closes all my Firefoxes first, like this:

#!/bin/bash

# Prerequisites:
# sudo apt-get install sysvinit-utils xdotool

set -x
set -u

function close_firefoxes()
{
    local PID
    local WID

    PID=$(pidof -s firefox)
    FOUND=$?

    while [ $FOUND ]; do
    {
        WID=$(xdotool search --pid "$PID" | tail -1)
        xdotool windowactivate --sync "$WID"
        xdotool key --clearmodifiers 'ctrl+q'
        sleep 1
        PID=$(pidof firefox)
        FOUND=$?
    }; done
}

close_firefoxes

mate-session-save --shutdown-dialog

Elm Basics Video

Series: Snake in Elm, Elm makes me happy, Elm Basics

A lot of the documentation about the new language I am really excited about, Elm focusses on the Elm Architecture and the ideas of Functional Reactive Programming, and while those are the fundamental reasons I am interested in Elm, I found myself stuck on the syntax quite often.

So, in this video I review almost all the syntax and basic ideas you need to be able to read and write Elm code, treating it as a general programming language.

Update: forgot to add the slides – here they are:
Slides: Elm Basics