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@heathermiller
heathermiller / scala-cheatsheet.md
Last active May 11, 2024 14:06
Scala Cheatsheet

This cheat sheet originated from the forum, credits to Laurent Poulain. We copied it and changed or added a few things.

Evaluation Rules

  • Call by value: evaluates the function arguments before calling the function
  • Call by name: evaluates the function first, and then evaluates the arguments if need be
    def example = 2      // evaluated when called
    val example = 2      // evaluated immediately
@garnaat
garnaat / gist:2917662
Created June 12, 2012 13:55
Example using boto to create an IAM role and associate it with an EC2 instance
In [1]: policy = """{
...: "Statement":[{
...: "Effect":"Allow",
...: "Action":["s3:*"],
...: "Resource":["arn:aws:s3:::mybucket"]}]}"""
In [2]: import boto
In [4]: c = boto.connect_iam()
In [5]: instance_profile = c.create_instance_profile('myinstanceprofile')
In [6]: role = c.create_role('myrole')
In [7]: c.add_role_to_instance_profile('myinstanceprofile', 'myrole')
@jboner
jboner / latency.txt
Last active July 4, 2024 04:27
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