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Falsehoods programmers believe about prices

  1. You can store a price in a floating point variable.
  2. All currencies are subdivided in 1/100th units (like US dollar/cents, euro/eurocents etc.).
  3. All currencies are subdivided in decimal units (like dinar/fils)
  4. All currencies currently in circulation are subdivided in decimal units. (to exclude shillings, pennies) (counter-example: MGA)
  5. All currencies are subdivided. (counter-examples: KRW, COP, JPY... Or subdivisions can be deprecated.)
  6. Prices can't have more precision than the smaller sub-unit of the currency. (e.g. gas prices)
  7. For any currency you can have a price of 1. (ZWL)
  8. Every country has its own currency. (EUR is the best example, but also Franc CFA, etc.)
' Copyright (c) 2007, Tony Ivanov
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@willurd
willurd / web-servers.md
Last active September 1, 2025 05:45
Big list of http static server one-liners

Each of these commands will run an ad hoc http static server in your current (or specified) directory, available at http://localhost:8000. Use this power wisely.

Discussion on reddit.

Python 2.x

$ python -m SimpleHTTPServer 8000
@spion
spion / a-warning.md
Last active April 19, 2025 05:17
C++ versus V8 versus luajit versus C benchmark - (hash) tables

Warning

This benchmark has been misleading for a while. It was originally made to demonstrate how JIT compilers can do all sorts of crazy stuff to your code - especially LuaJIT - and was meant to be a starting point of discussion about what exactly LuaJIT does and how.

As a result, its not indicative of what its performance may be on more realistic data. Differences can be expected because

  1. the text will not consist of hard-coded constants
@jboner
jboner / latency.txt
Last active September 9, 2025 11:52
Latency Numbers Every Programmer Should Know
Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference 0.5 ns
Branch mispredict 5 ns
L2 cache reference 7 ns 14x L1 cache
Mutex lock/unlock 25 ns
Main memory reference 100 ns 20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy 3,000 ns 3 us
Send 1K bytes over 1 Gbps network 10,000 ns 10 us
Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD
# Author: Pieter Noordhuis
# Description: Simple demo to showcase Redis PubSub with EventMachine
#
# Update 7 Oct 2010:
# - This example does *not* appear to work with Chrome >=6.0. Apparently,
# the WebSocket protocol implementation in the cramp gem does not work
# well with Chrome's (newer) WebSocket implementation.
#
# Requirements:
# - rubygems: eventmachine, thin, cramp, sinatra, yajl-ruby