December 17, 2018

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sharkdp/insect

sharkdp/insect

High precision scientific calculator with support for physical units
repo name sharkdp/insect
repo link https://github.com/sharkdp/insect
homepage https://insect.sh
language PureScript
size (curr.) 1952 kB
stars (curr.) 2003
created 2017-02-25
license MIT License

insect

A high precision scientific calculator with full support for physical units.

Try the web version here: https://insect.sh

Contents

Documentation

  • Evaluate mathematical expressions:

    1920/16*9
2^32
sqrt(1.4^2 + 1.5^2) * cos(pi/3)^2

    • Operators: addition (+), subtraction (-), multiplication (*, ·, ×), division (/, ÷, per), exponentiation (^, **). Full list: see Reference below.

    • Mathematical functions: abs, acos, acosh, asin, asinh, atan, atan2, atanh, ceil, cos, cosh, exp, floor, fromCelsius, fromFahrenheit, gamma, ln, log, log10, maximum, minimum, mean, round, sin, sinh, sqrt, tan, tanh, toCelsius, toFahrenheit.

    • High-precision numeric type with 30 significant digits that can handle very large (or small) exponents like 10^(10^10).

    • Exponential notation: 6.022e23.

  • Physical units: parsing and handling, including metric prefixes:

    2 min + 30 s
40 kg * 9.8 m/s^2 * 150 cm
sin(30°)

    • Supported units: see Reference section below.

    • Implicit conversions: 15 km/h * 30 min evaluates to 7.5 km.

    • Useful error messages:

      > 2 watts + 4 newton meter

Conversion error:
  Cannot convert unit N·m (base units: kg·m²·s⁻²)
              to unit W (base units: kg·m²·s⁻³)

  • Explicit unit conversions: the -> conversion operator (aliases: →, ➞, to):

    60 mph -> m/s
500 km/day -> km/h
1 mrad -> degree
52 weeks -> days
5 in + 2 ft -> cm
atan(30 cm / 2 m) -> degree
6 Mbit/s * 1.5 h -> GB

  • Variable assignments:

    Example: mass of the earth

    r = 6000km
vol = 4/3 * pi * r^3
density = 5 g/cm^3
vol * density -> kg

    Example: oscillation period of a pendulum

    len = 20 cm
2pi*sqrt(len/g0) -> ms

    • Predefined constants (type list to see them all): speed of light (c), Planck’s constant (h_bar), electron mass (electronMass), elementary charge (elementaryCharge), magnetic constant (µ0), electric constant (eps0), Bohr magneton (µ_B), Avogadro’s constant (N_A), Boltzmann constant (k_B), gravitational acceleration (g0), ideal gas constant (R), …

    • Last result: you can use ans (answer) to refer to the result of the last calculation.

  • User-defined functions:

    Example: kinetic energy

    kineticEnergy(mass, speed) = 0.5 * mass * speed^2 -> kJ

kineticEnergy(800 kg, 120 km/h)

    Example: barometric formula

    P0 = 1 atm
T0 = fromCelsius(15)
tempGradient = 0.65 K / 100 m

pressure(height) = P0 * (1 - tempGradient * height / T0)^5.255 -> hPa

pressure(1500 m)

  • Sums and products:

    Syntax:

    sum(<expression>, <index-variable>, <from>, <to>)
product(<expression>, <index-variable>, <from>, <to>)

    Examples:

    # sum of the first ten squares
sum(k^2, k, 1, 10)

# the factorial of n as the product 1 × 2 × ... × n
myFactorial(n) = product(k, k, 1, n)

  • Unicode support:

    λ = 2 × 300 µm
ν = c/λ → GHz

  • And more: tab completion, command history (arrow keys, Ctrl+R), pretty printing, syntax highlighting, …

Reference

Pros and cons

Reasons to use Insect

  • Insect is open source.
  • There is a web version that requires no installation.
  • With both browser and terminal versions available, insect is truly cross-platform.
  • Insect has first-class support for physical units, including metric and binary prefixes. While evaluating your calculation, Insect ensures that you did not accidentally make any mistakes in combining the physical quantities.
  • Insect supports an interactive style with its readline-based interface. There is a saved history that can be browsed by pressing up- and down keys. The history is also searchable via Ctrl-R.
  • The syntax of Insect is rather strict. The parser does not try to be “smart” on syntactically incorrect input, so there shouldn’t be any surprises - and you can trust the result of your calculation. The parsed user input is always pretty-printed for a quick double-check.
  • Insect is written in PureScript and therefore benefits from all the safety-guarantees that a strictly-typed functional programming language gives you.
  • The source code of purescript-quantities (the underlying library for physical units) as well as the code of Insect itself is extensively tested.

Reasons to choose an alternative

  • Insect is a scientific calculator. It’s not a computer algebra system that solves differential equations or computes integrals. Try WolframAlpha instead.
  • There is no graphical user interface with buttons for each action (x², 1/x, DEG/RAD, etc.). Qalculate! is a fantastic tool that supports both text- as well as graphical input.
  • Insect supports a huge range of physical units: all SI units, all units that are accepted by SI as well as most units of the imperial and US customary systems (and many more). However, if you need something even more comprehensive, try GNU units.
  • Insect is not a general-purpose programming language. You could try Frink.
  • Insect does not have a special mode for hexadecimal or binary numbers (yet).

FAQ

  • Why are Celsius and Fahrenheit not supported?

    Compared to the SI unit Kelvin and in contrast to all other units, Celsius and Fahrenheit require an additive offset when converting into and from other temperature units. This additive offset leads to all kinds of ambiguities when performing calculations in these units. Adding two temperatures in Celsius, for example, is only meaningful if one of them is seen as an offset value (rather than an absolute temperature). Insect is primarily a scientific calculator (as opposed to a unit conversion tool) and therefore focuses on getting physical calculations right.

    Even though °C and °F are not supported as built-in units, there are helper functions to convert to and from Celsius (and Fahrenheit):

    • fromCelsius takes a scalar value that represents a temperature in Celsius and returns a corresponding temperature in Kelvin:

      > fromCelsius(0)

   = 273.15 K

> k_B * fromCelsius(23) to meV

   = 25.5202 meV

    • toCelsius takes a temperature in Kelvin and returns a scalar value that represents the corresponding temperature in Celsius:

      > toCelsius(70 K)

   = -203.15

> toCelsius(25 meV / k_B)

   = 16.963

  • Why is 1/2 x parsed as 1/(2x)?

    Implicit multiplication (without an explicit multiplication sign) has a higher precedence than division (see operator precedence rules). This is by design, in order to parse inputs like 50 cm / 2 m as (50 cm) / (2 m). If you meant ½ · x, write 1/2 * x.

  • What is the internal numerical precision?

    By default, Insect shows 6 significant digits in the result of the calculation. However, the internal numerical precision is much higher (30 digits).

  • How does the conversion operator work?

    The conversion operator -> attempts to convert the physical quantity on its left hand side to the unit of the expression on its right hand side. This means that you can write an arbitrary expression on the right hand side (but only the unit part will be extracted). For example:

    # simple unit conversion:
> 120 km/h -> mph

  = 74.5645 mi/h

# expression on the right hand side:
> 120 m^3 -> km * m^2

  = 0.12 m²·km

# convert x1 to the same unit as x2:
> x1 = 50 km / h
> x2 = 3 m/s -> x1

  x2 = 10.8 km/h

  • What is the relation between the units RPM, rad/s, deg/s and Hz?

    The unit RPM (revolutions per minute) is defined via 1 RPM = 1 / minute where the 1 on the right hand side symbolizes “1 revolution”.

    As the base unit is the same (1 / second), RPM can be converted to rad / s, deg / s or Hz. Note, however, that 1 RPM does not equal 2π rad / min or 360° / min or 1 Hz, as some might expect. If you interested in computing the traversed angle of something that rotates with a given number of revolutions per minute, you need to multiply by 2π rad or 360 ° because:

    1 RPM · (360°/revolution) = (1 revolution / minute) · (360° / revolution) = 360° / minute

Terminal version

In addition to the web interface, there is also a command line version which can by installed via npm:

npm install -g insect

Note that this might fail if you run it with sudo. Instead, set up a prefix directory and call npm install as a user.

If you prefer not to install nodejs and npm, you can use one of the standalone binaries on the release page.

For Arch Linux, there is a package on AUR:

yaourt -S insect

On Fedora 28+, you can install insect from the official sources:

sudo dnf install insect

For Fedora versions 26 and 27, you need to enable this copr repository:

sudo dnf copr enable fnux/insect

For macOS, there is a Homebrew package:

brew install insect

Development

BuildStatus

Insect is written in PureScript (see Getting Started guide). You can install all dependencies and build the whole project by running:

npm install
npm start

Open web/index.html in your browser.

Insect comes with a comprehensive set of unit tests. You can run them by calling

npm test
purescript
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