2025-08-15
Save the calculator source code. And start a NodeJS REPL:
node --require ./calc.js
Your path may end up different, but your folder structure is obviously up to you. ~/scripts/ would be reasonable.
The idea here is to use NodeJS as a predictable calculator. You may just use node and leave it at that. But to cut down on keystrokes, we can include a script with useful global properties, mainly from the Math object. There will always be a clear history of what happened in the scrollback, especially if we avoid mutating variables. You won't quite have the convenience of the last answer, e.g. * 2, but you can quickly retrieve previous expressions with the up arrow or store values with const or let. We can also rename things, like Math.log() might be more familiar as ln() to be clear that it is the natural logarithm and to reserve log() for console printing.
Trigonometry is a good use for a calculator. Here is a function to use the popular 360-degree system:
global.sin = Math.sin
global.sindeg = (a) => sin(tau * a / 360)
global.tau = 2 * Math.PI
What about floating point issues? You can of course choose to ignore them, or you may make use of toPrecision, which we can define as something shorter like pr() or pr1():
global.pr = (d, x) => x.toPrecision(d)
global.pr1 = pr.bind(null, 1)
I tend to do the raw calculation first, and then adjust for significant figures (or any other desired precision) if the result turns out ugly.
> .1+.2
0.30000000000000004
> (.1+.2).toPrecision(1)
'0.3'
> pr(1, .1+.2)
'0.3'
> pr1(.1+.2)
'0.3'
To avoid having to retype the command, create an alias for it.
alias calc="node --require ~/scripts/calc.js"
If you're curious how other commands work, they are stored in files without an extension in a directory listed in the PATH environment variable. The Free Desktop standard recommends using a hidden folder in your home directory. I had higher hopes for /usr/bin, but the permissions really discouraged me.
node --require ~/scripts/calc.js
export PATH=$HOME/.local/bin:$PATH