Gecko

An interactive REPL devised for quickly getting calculations done.

Use Gecko from source by running gecko.py (with the command gecko.py, python3 gecko.py, etc.) to start the REPL.
Requires Python 3.6 or higher.
Read DEVELOPMENT.md for further information on standalone builds / dev info.

Features

Clean expression syntax

Write them as you would using pencil and paper (sort of).

Straightforward piping for intricate expressions

Write down your math as it comes to your head!

Built-in math functions and constants

Wanna use pi? Just type pi. Wanna use sin? Just type sin.

Custom functions

Define your own functions, if you will!

Complex numbers support

Gecko couldn't be less.

Ans feature

This thing we all miss from scientific calculators...

Calc command

No need to re-type the expression, just calc your variable again!

Var dump

Hmst, I do wonder, what variables have I assigned so far?

Integrals

Bye-bye to WolframAlpha for scalar function integrals!

Plots

Bye-bye to Desmos and GeoGebra for scalar function plots!

Expression reducer operator ("parentheses saver")

"Never press the left-arrow", says Gecko. This can save you a few keystrokes, if you wrap your mind around it.

Gecko REPL feature description

"Let's break Gecko", they said.
Here I provide a more complete (yet not at all technical) description of all of Gecko's features.

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Statements are the big 'blocks' that make up Gecko.
They are like commands that you enter to the REPL for Gecko to eat. Like bugs. Yum.
Multiple Statements are separated by a semicolon or by newline.

Everything Gecko understands is the following:

Statements

I will list them, followed by an arrow like this -> and the explanation of what they do.

• Any valid expression (see next section)
• Variable assignments
  • a=5 -> a=5
  • n1=n2=n3=15 -> n1=15, n2=15, n3=15
  • value = 2*3 + 1 -> value = 7
  • a = 5; b = 3+a -> b = 8
• Function definition
  • f(x,y) = x+y
  • g(x,y) = 2f(x,y)
• Plotting an expression (see Expressions)
  All these show a plot of the expression you write down, using x as the variable.
  • plot x^2 from 0 to 5
  • f(x)=2x-5; plot f(x) from -10 to 10 as line1
  • plot rt(x) from 0 to 100 as "root of x"
• calc command
  • a=2; d=10a; a=5; calc d -> d = 50
• polar command
  • d=5+3j; polar d, or
  • d=5+3j; d polar
  • Output: 5.831 @ 0.5404 rad (30.9638 deg)
• vars command
  shows all assigned global variables and their values
• new command
  resets all variables and functions

Expressions

I'll list all valid expressions, plus some examples of 'real-life' usage:

• Numbers
  • Real numbers, standard notation
    • -3
    • 14.27
    • 0.2
    • .001
  • Real numbers, scientific notation
    • 3e4
    • -2e-10
    • .02e3
  • Complex numbers
    • 4+2j
    • -0.3j + 3
    • rt(-16)+1
    • 3e5 + 5e10j
  • Complex number - polar notation
    • 14@0.5pi, absolute value 14, angle 0.5pi radians
    • 14 @ 0.5pi
    • 14@<90, absolute value 14, angle 90 degrees
    • 14 @ <90
    • 14 @< 90
• IDs
  • Made from any combination of letters, numbers, and _, starting with a non-number. They can store a value, just like variables do in most programming languages (or any?)
  • Examples are value, var1, total_result, n1, _1st_attempt, etc.
• Common binary operations:
  • + - * / ^
    • 5+3
    • 0.2^3
    • etc., you know this
• Unary minus:
  • a=2; result = -a -> result = -2
• Built-in math functions and constants
  • sin, cos, tan
    • inverse function by prepending a- (as in asin)
    • use degrees by appending -d (as in tand, acosd, etc.)
  • ln rt angle abs deg rad + pi e tau reassignable constants
    • Bonus: shorthand for abs(x) is |x|
• Implicit multiplication
  • 2x
  • 5sin(4)
  • 0.5(2+3)
  • 6x^3
  • (x-5)(x+10)
  • etc.
• with expression, when you feel like storing something in a variable but just for a bit
  • 2+a with a = 0.1 -> 2.1
  • 2alpha+gamma with alpha=6, gamma=2 -> 14
  • Temporary variables assigned in with statements are not stored!
• then expression, when you want to write down math as it comes to your head
  • 3^2+4^2 then rt(x) -> 5
  • x = 10; result = 14-2^2 then 'var x/var' -> result = 1 (var could be replaced by any other valid ID)
• Function calls
  • sum(x,y)=x+y; sum(5,6) -> 11
  • mult(x,y)=x*y; square(x) = mult(x,x); square(10) -> 100
  • double(x)=2x; double(double(3)) -> 12
  • Notice: the variables and functions namespace is disjoint, meaning you can have a variable called sum with a value of 69, and also a function called sum doing something else, with no problems at all. Not adviced, but works.
  • sum=10; sum(x,y)=x+y; sum(sum,sum(sum,sum)) -> 30
• Integrals
  • int x from 0 to 5 -> 12.5
  • f(x)=sin(x); int f(x)+1 from 0 to pi -> 5.1416
• $ operand to save parentheses (you can ignore this if you don't get it now)
  Basically, whenever Gecko finds a $, it just takes the bribe and reduces whatever you had already typed, as if you pressed 'Enter', but you can keep typing.
  • 1+2 $ * 10 -> 30
  • int x from 0 to 1 $ + int x from 4 to 5 == (int x from 0 to 1) + (int x from 4 to 5)
• Special ans ID, stores last printed value or 0
  • a=10 -> ans = 0
  • a=10; 15a -> ans = 150
  • sin(4^2); result = 10ans -> result = 10sin(4^2)

Motivation

As an engineering student, I've faced the task of repeating similar or identical calculations for problem solving way too often. Or just, a random piece of math I wanted to quickly solve and carry on doing something else. Maybe a simple plot I wanted to take a look at, or a silly single-variable integral.

Quickly is the key here. I wanted to know the result as fast as possible, typing as little as I could, waiting the least as I could.

Using a scientific calculator was not ideal. It was too slow and kinda awkward to type long expressions, usually low on battery, and I had to find it in the first place.

The Python interpreter was alright, but I didn't like typing ** for powers, 2*x stuff, having to import the math module whenever I opened the terminal...

Also, I couldn't use the ANS button that my scicalc had.
Often, I found myself typing out formulas on-the-spot, having to go back and forth on the command line adding symbols.

Plots? Type them on Google, or Desmos, or GeoGebra, or WolframAlpha. Same as integrals. Kinda slow, Internet connection dependant, and so on.

I mean, just look at this situation

Say I had to solve for x in x² = a+b*c^15/9e9.
I would first type a+b*c**15/9e9. Then realise. Oh.

I have to take the square root of all this.
Go back.
Hit the left-arrow key so many times.
Add the sqrt( at the start. Ok.
Then the ) at the end.

Nevermind. I didn't import the math module yet.

S L O W.

My dream was something like:

stuff_i_want = a+b*c**15/9e9 then sqrt(ans) # nothing like this available

Also, if I wanted to perhaps tweak the value of, say, a, I'd have to re-type all the equation, or find out where in the command history it was left.

Switching to the Julia <3 interpreter solved several of these issues, with its beautifully clean syntax, also adding new features such as:

f(x) = 2x^2+x-14 # Lovely, I just defined a function! (Lemme copy this syntax)

And I could use the pipe operator to imitate what I wanted to achieve - writing down the formula in the order that it came to my mind:

result = a+b*c^15/9e9 |> x->sqrt(x)

Gorgeous. A bit strange to type rapidly (|> x-> would get my fingers entangled somewhat often), but it was pretty neat.

Julia also has built-in math functions, which I simply loved. No more from math import * at the start, or no more ugly cos(radians(thing))!!!! AND the ANS feature!!! What a beast.

Still, no solution for the 're-calc' issue...

And no way of finding roots for quadratic formulas quickly...
Or just zeros of a function...
Too many parentheses...
No easy command to find the polar representation of a complex number...
Not really any way to natively do plots...
Neither easily calculating integrals...

I had to take action.

This is when Gecko came to be. 🦎

I decided to take all the features of the Julia REPL that I absolutely loved, and add to those my own needs (and dreams ).
Aaand the nice looking Gecko ASCII art at the start. Credit to Andreas Freise for it, it's super cute.

Thanks to

David Beazley for the Sly Lex Yacc tool. It is wonderful and really easy to use. Definitely couldn't (or wouldn't) have done this without it.

Andreas Freise for the Gecko ASCII art.

Julia creators for making that wonder. Many features of my REPL have been inspired in yours.

People in ggg for testing.

Guido from the past for making this.

You for reading. Thanks.