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Digital cryptography! This is a subject I've been interested in since taking a class with Prof. Fred Schneider back in college. Articles pop up on Hacker News fairly often that pique my interest and this technique is the result of one of them.
Specifically, this is about Lamport signatures. There are many signature algorithms (ECDSA and RSA are the most commonly used) but Lamport signatures are unique because they are formed using a hash function. Many cryptographers believe that this makes them resistant to attacks made possible by quantum computers.
List some crypto libraries for JavaScript out there. Might be a bit out dated. Scroll to the bottom.
http://www.w3.org/TR/WebCryptoAPI/
This specification describes a JavaScript API for performing basic cryptographic operations in web applications, such as hashing, signature generation and verification, and encryption and decryption. Additionally, it describes an API for applications to generate and/or manage the keying material necessary to perform these operations. Uses for this API range from user or service authentication, document or code signing, and the confidentiality and integrity of communications.
| int[][] result; | |
| float time; | |
| void draw() { | |
| for (int i=0; i<width*height; i++) | |
| for (int a=0; a<3; a++) | |
| result[i][a] = 0; | |
| for (int sa=0; sa<samplesPerFrame; sa++) { | |
| time = map(frameCount-1 + sa*shutterAngle/samplesPerFrame, 0, numFrames, 0, 1); |
Here're a couple of examples demonstrating the generative semantics of SML exceptions (derived from http://mlton.org/GenerativeException) followed by their analogues in OCaml:
This post also appears on lisper.in.
Reader macros are perhaps not as famous as ordinary macros. While macros are a great way to create your own DSL, reader macros provide even greater flexibility by allowing you to create entirely new syntax on top of Lisp.
Paul Graham explains them very well in [On Lisp][] (Chapter 17, Read-Macros):
The three big moments in a Lisp expression's life are read-time, compile-time, and runtime. Functions are in control at runtime. Macros give us a chance to perform transformations on programs at compile-time. ...read-macros... do their work at read-time.
| module Fib using: Platform where | |
| open Platform Prelude expose [+, parse, as-string, ~] | |
| open Platform List expose [zip:using:, map:, take:, filter:, sum] | |
| open Platform IO expose [read-line, print] | |
| -- Typing things is currently cumbersome, but the type inference algorithm should catch 90% of this | |
| let (Num a) => String -> a :: | |
| x as-number = x parse |
Write a program in your favourite programming language to compute the sum of the first N even numbers in the Fibonacci sequence, then display the sum of its digits.
E.g.: Where N = 5, the answer is 17, since:
| /* | |
| [DESAFIO / LANGUAGE WAR] Implemente um programa na sua linguagem favorita onde o usuário digita um número x, e o programa calcula o somatório dos x primeiros números pares da sequência fibonacci, e imprime a soma dos algarismos desse número. | |
| Por exemplo, quando x = 5, a resposta é 17, pois: | |
| 1. A sequência fibonacci é 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233,... | |
| 2. Os 5 primeiros números pares são 0, 2, 8 e 34, 144. | |
| 3. O somatório disso é 188. | |
| 4. Somando os algarismos, 1+8+8 = 17 |
