Profile

Scrapbook photo 1
Scrapbook photo 2
Scrapbook photo 3
Scrapbook photo 4
Scrapbook photo 5
Luca Luve
1,537 followers|215,870 views
AboutPosts

Stream

Luca Luve

Shared publicly  - 
 
How Functional Programming Mattered
by Zhenjiang Hu, John Hughes and Meng Wang

Abstract
In 1989 when functional programming was still considered a niche topic, Hughes wrote a visionary paper arguing convincingly “why functional programming matters”. More than two decades have passed. Has functional programming really mattered? Our answer is a resounding “Yes!”. Functional programming is now at the forefront of a new generation of programming technologies, and enjoying increasing popularity and influence. In this paper, we review the impact of functional programming, focusing on how it has changed the way we may construct programs, the way we may verify programs, and fundamentally the way we may think about programs.

--- --- ------ --- ------ --- ------ --- ------ --- ------ --- ------ --- ------ --- ---

For those who are interested, here is the cited paper:
Why Functional Programming Matters by John Hughes
http://www.cse.chalmers.se/~rjmh/Papers/whyfp.html
2
Add a comment...

Luca Luve

Shared publicly  - 
 
 
Ham Radio  operator David Larsen KK4WW  had opportunities to collect Soviet computers and operate amateur radio during dozens of visits to the Soviet Union and Former Soviet Countries during the 1990/s. One visit has a special memory for Daavid  because Jerry Scheeler a professional film maker traveled with our group for 3 weeks in 1993 and made a nice documentary film . You can see the film here. https://www.youtube.com/watch?v=ALSirXDJ42w
1 comment on original post
1
Add a comment...

Luca Luve

Shared publicly  - 
 
 
Korea Telecom now offers a 1 Gbps mobile Internet service, achieved by using Multpath TCP to combine LTE and WiFi. They run a SOCKSv5 proxy in their datacenter to enable Multipath TCP for all websites. Currently supports Samsung Galaxy S6 & Edge phones.

So I guess all those "the web is so much faster in Korea" jokes are true ...
View original post
1
Add a comment...

Luca Luve

Shared publicly  - 
 
 
Galileo Almost Discovered General Relativity

We all know the (probably apocryphal [1]) story. Galileo, all around physics bad-ass, dropped a bowling ball and a feather off of the Leaning tower of Pisa. But did you know this is a hint of general relativity? (To read this story in blog form go here: http://www.thephysicsmill.com/2015/07/26/galileo-almost-discovered-general-relativity/)

Galileo found that objects of vastly different weights, like bowling balls and feathers for example, would fall at exactly the same rate and hit the ground at exactly the same time. Air resistance gets in the way, of course. But if you perform the experiment in vacuum, as these guys did, then you do find the bowling ball and the feather land at exactly the same time:

https://youtu.be/E43-CfukEgs

This leads to a fundamental truth we’ve all memorized in school: The acceleration due to gravity is constant. But there’s a more fundamental truth underneath that one, a truth that sat unrecognised until the time of Einstein: Gravity is not a force. To get the full story, you’ll need to wait until next time, when I start to describe general relativity. But for now, let’s explore how Galileo’s experiment shows that gravity is incredibly special.

Electric Bowling Ball, Electric Feather

To understand why gravity is weird, we have to understand how the other forces work. So let’s set up an experiment analogous to Galileo’s, but with electricity, and see what happens. So here’s the experiment (shown in figure 2 ).

We take two metal plates out into space, far enough away that there’s no gravity. Then we connect the plates to a battery so that one plate gets a positive charge (red) and one gets a negative charge (blue). This creates a constant electric field, much like the constant gravitational field near the Earth. Finally, we place two particles of equal mass at rest at the same position between the plates. We give one particle a very large positive charge (right), and one particle a smaller positive charge (left). Like charges attract and opposite charges repel, so both particles will move towards the blue plate.

The particle on the right will absolutely reach the plate before the particle on the left.

Okay, that’s strange. In this experiment, electric charge played the role of “mass” in the sense that it controls how strong the electric force that acts on the particles is. In electromagnetism, unlike in gravity, the stronger force resulted in a bigger acceleration. But is that the whole story? To find out, let’s try the same experiment, but with a twist.

Electric Dumb-bell

Let’s take the same battery-powered metal plates into space. But this time, we put two particles of equal electric charge between the plates, as shown in figure 3. But we give one particle (on the left) much more mass by attaching some extra weights to it. Now the electric forces on the two particles are the same. Should they fall at the same rate?

Not so fast. Now the less massive particle (on the right) falls faster.

There Are Two Types of Mass

What we’ve discovered with these two experiments is that there are two types of mass. There’s the gravitational mass, which controls how strong the force of gravity is for a particular object. This is directly analogous to electric charge. The bigger an electric charge, the bigger the electric force. The bigger a gravitational mass, the stronger gravity is. This is what we saw in our first experiment.

But there’s also the inertial mass. This mass controls how difficult it is to change an object’s motion. This is the mass in Newton’s second law of motion, F=ma. The bigger the mass is, the more force is required to move it. We all know this intuitively: the heavier an object, the harder it is to push. This is what we observed in our second experiment. More mass means less motion.

But when Galileo performed his experiment at Pisa, he discovered something incredible: for gravity and only gravity, these two types of mass are the same. This is unlike every other force. The electromagnetic force, the strong force, and the weak force, all have a charge, which controls how strong the force is, that is separate from their inertial mass. But the gravitational “charge” is the same as the inertial mass.

And if you allow inertial and gravitational mass to be the same, something changes. Instead of “the gravitational field due to the Earth is the same everywhere,” we get “the acceleration due to the gravity of the Earth is always the same everywhere.”

Gravity becomes the same as acceleration.

That’s very weird. And very special. And it is this fact that lead Einstein to develop general relativity. But through his experiment, Galileo almost found it first.

To learn how this leads to general relativity. Tune in next week.

Related Reading

The thought experiments I described here are modifications of Einstein’s famous elevator thought experiments. You can find many descriptions of those thought experiments online. Here’s a few:

1. I wrote about Einstein's elevator once before. Here's the link: http://www.thephysicsmill.com/2012/12/02/ftl-part-3-general-relativity-shortcuts/

2. Here's a cool video demonstration of the elevator at work, and how gravity and acceleration are one and the same:
https://youtu.be/sbSxxsb30_E

3. And here's a wonderful article by +Paul Halpern  on the history of the thought experiment:
https://medium.com/starts-with-a-bang/life-in-a-freely-falling-elevator-746ddca2d020

references
[1] http://www.thehindu.com/seta/2005/06/30/stories/2005063000351500.htm

#physics #science #ScienceSunday #ScienceEveryDay #hipster  
19 comments on original post
1
Add a comment...

Luca Luve

Shared publicly  - 
 
Modern C++
std::shared_ptr's secret constructor

It allows us to construct a new shared_ptr instance that shares ownership with another shared_ptr, but which has a different pointer value.

Curious? Read this nice and short post by +Anthony Williams
 
Aliasing shared_ptrs allow you to pass out shared_ptr objects that refer to subobjects and keep the parent alive.
View original post
3
Add a comment...
Have them in circles
1,537 people
jerry chan's profile photo
PetGuide.com's profile photo
Raj Brainguru's profile photo
igor kel's profile photo
John Proffer's profile photo
Pawan Khatri's profile photo
BANDAR TOGEL terpercaya's profile photo
Namit Dumre's profile photo
Jared Byer's profile photo

Luca Luve

Shared publicly  - 
 
Automated reasoning in F#, Scala, Haskell, C++, and Julia
Automated reasoning in F#, Scala, Haskell, C++, and Julia. Tweet. 2015.04.05. We need to simplify the following expression: \[e = (1 + 0 \times x) \times 3 + 12.\]. Luckily for us, we won't have to remember any elementary school arithmetic, because Harris' excellent Handbook of Practical Logic ...
4
1
Mouhammad Fakhoury's profile photo
Add a comment...

Luca Luve

Shared publicly  - 
 
 
Prisons in Japan are filling up with an unexpected group: the elderly http://econ.st/1grzmNh
8 comments on original post
1
Add a comment...

Luca Luve

Shared publicly  - 
 
 
marketing for dummies

1- You see a gorgeous girl at a party. You approach her and say "I'm rich, marry me." - That's DIRECT MARKETING.

2- You attend a party and your friend approaches a gorgeous girl and says "That's my friend. He is very rich. Marry him." - That's ADVERTISING.

3- You attend a party and a gorgeous approaches you. She says "You are very rich. Marry me."  - That's BRAND RECOGNITION.

4- You approach a gorgeous girl at a party. You explain to her that you are very rich and that she should marry you. She slaps you in response. - That's CUSTOMER FEEDBACK.

5- You approach a gorgeous girl at a party and explain to her that you are very rich and that she should marry you. She introduces her husband. - That's DEMAND & SUPPLY GAP.

6- You see a gorgeous girl at a party and just as you are about to approach her, your wife arrives. - That's RESTRICTION FROM ENTERING NEW MARKET.

#marketing  
1 comment on original post
2
1
Andy Lo's profile photo
Add a comment...

Luca Luve

Shared publicly  - 
 
 
Inserting into AVL trees in sorted order preserves perfect balance. Who knew? (Probably someone knew, but not me.)
One of my students, Will Devanny, is teaching a summer-session offering of our lower-division undergraduate data structures class. (My university forbids graduate students from being the instructor of record for classes during the regular term, despite allowing equally-qualified non-student…
2 comments on original post
2
Add a comment...

Luca Luve

Shared publicly  - 
 
HORNET: High-speed Onion Routing at the Network Layer

We present HORNET, a system that enables high-speed end-to-end anonymous channels by leveraging next generation network architectures. HORNET is designed as a low-latency onion routing system that operates at the network layer thus enabling a wide range of applications. Our system uses only symmetric cryptography for data forwarding yet requires no per-flow state on intermediate nodes. This design enables HORNET nodes to process anonymous traffic at over 93 Gb/s. HORNET can also scale as required, adding minimal processing overhead per additional anonymous channel. We discuss design and implementation details, as well as a performance and security evaluation.
Abstract: We present HORNET, a system that enables high-speed end-to-end anonymous channels by leveraging next generation network architectures. HORNET is designed as a low-latency onion routing system that operates at the network layer thus enabling a wide range of applications.
1
Add a comment...
People
Have them in circles
1,537 people
jerry chan's profile photo
PetGuide.com's profile photo
Raj Brainguru's profile photo
igor kel's profile photo
John Proffer's profile photo
Pawan Khatri's profile photo
BANDAR TOGEL terpercaya's profile photo
Namit Dumre's profile photo
Jared Byer's profile photo
Work
Skills
I “talk” to computers and lead people
Links
YouTube
Story
Tagline
Software "Gardener"/Software Craftsman. Knowledge-Hungry Learner. Constanter et non trepide.
Introduction
Constanter et non trepide.

It is not knowledge, but the act of learning, not possession but the act of getting there, which grants the greatest enjoyment. When I have clarified and exhausted a subject, then I turn away from it, in order to go into darkness again; the never-satisfied man is so strange if he has completed a structure, then it is not in order to dwell in it peacefully, but in order to begin another. I imagine the world conqueror must feel thus, who, after one kingdom is scarcely conquered, stretches out his arms for others. — J. C. F. Gauß (Letter to Farkas (Wolfgang) Bolyai, 1808)

Dimidium facti, qui coepit, habet: sapere aude, incipe — Quintus Horatius Flaccus (Epistulæ I, ii, 40)

Historia vero testis temporum, lux veritatis, vita memoriæ, magistra vitæ, nuntia vetustatis — Marcus Tullius Cicĕro (De Oratore II, ix, 36)
Bragging rights
I have “contributed to the construction of the tunnel between CERN and Gran Sasso Laboratories” (about 730 km!) - http://goo.gl/aOYsd
Basic Information
Other names
Zero Knowledge, 0Knowledge, zer0k, ZK