A minimalist calculator for fermi estimation

This project contains a minimalist command-line calculator for Fermi estimation. For now, it just multiplies lognormals.

Motivation

Sometimes, Squiggle, simple squiggle or squiggle.c are still too complicated and un-unix-like.

Usage

Here is an example

$ go run f.go
5000000 12000000
=> 5000000.0 12000000.0
0.002 0.01
=> 13859.5 86583.4
30 180
=> 706832.8 9167656.0
/ 48 52
=> 14139.1 183614.7
/ 5 6
=> 2573.1 33632.0
/ 6 8
=> 368.4 4893.5
/ 60
=> 6.1 81.6

Perhaps this example is more understandable with comments and better units:

$ sed -u "s|#.*||" | sed -u 's|M|000000|g' | go run f.go
5M 12M # number of people living in Chicago
=> 5000000.0 12000000.0
0.002 0.01 # fraction of people that have a piano
=> 13859.5 86583.4
30 180 # minutes it takes to tune a piano, including travel time
=> 706832.8 9167656.0
/ 48 52 # weeks a year that piano tuners work for
=> 14139.1 183614.7
/ 5 6 # days a week in which piano tuners work
=> 2573.1 33632.0
/ 6 8 # hours a day in which piano tuners work
=> 368.4 4893.5
/ 60 # minutes to an hour
=> 6.1 81.6
# ^ piano tuners in Chicago

You can see a recording in action here:

Installation

make build
sudo make install
f # rather than the previous go run f.go

Why use make instead of the built-in go commands? Because the point of make is to be able to share command-line recipes.

Usage together with standard Linux utilities

f
sed -u "s|#.*||" | sed -u 's|M|000000|g' | f

cat more/piano-tuners.f | f
cat more/piano-tuners-commented.f | sed -u "s|#.*||" | sed -u 's|M|000000|g' | f

tee -a input.log | go run f.go | tee -a output.log
tee -a io.log | go run f.go | tee -a io.log

function f(){
  sed -u "s|#.*||" | 
  sed -u "s|//.*||" | 
  sed -u 's|K|000|g' | 
  sed -u 's|M|000000|g' | 
  sed -u 's|B|000000000|g' | 
  /usr/bin/f
}

Note that these sed commands are just hacks, and won't parse e.g., 3.5K correctly—it will just substitute for 3.5000

Tips & tricks

Conceptually clearer to have all the multiplications first and then all the divisions

Roadmap

• Write README
• Add division?
• Read from file?
• Save to file?
• Allow comments?
  • Use a sed filter?
• Add show more info version
• Scalar multiplication and division
• Program into a small device, like a calculator?
• Think of some way of calling bc
• Think how to integrate with squiggle.c to draw samples
• Think about how to draw a histogram from samples
• Display output more nicely, with K/M/B/T
• Consider the following: make this into a stack-based DSL, with:
  • Variables that can be saved to and then displayed
  • Other types of distributions, particularly beta distributions? => But then this requires moving to bags of samples. It could still be ~instantaneous though.

Some possible syntax for a more expressive stack-based DSL

1B to 20B
* 1 to 100
/ beta(1, 2)
=: x # content of the stack at this point saved into x

1 to 10
10 to 100
=: y # content of the stack at this point saved into y

x # put x on the stack
- y # substract y from the content of the stack. Requires interpreting x and y as list of samples