statecalc v0.1.11

StateCalc

About

StateCalc is a state based calculator interface that operates how you would expect a desktop or handled calculator to work. Digits are entered sequentially and can be processed with a handful of simple math functions.

StateCalc was intended to power gui calculators, but it is appropriate for any sequentially read sets of number or applied functions.

Main Example

"use strict";
import StateCalc from "statecalc";

let calc = new StateCalc();

calc.addNumber(2);
calc.equal();
calc.pw2();

calc.plus();
calc.addNumber(2);
calc.equal();

calc.plus();
calc.addNumber(2);
calc.equal();

console.log(calc.answer); // 8

Implementation Details

Overview

The interface is very simple and all private data is privately held using a symbol. However, it's important to note the difference in behavior for certain functions or states.

To manage internal state functions are split into two types, unary or binary.

Unary & Binary

The binary functions include all the primary arithmetic operations, plus (+), minus (-), divide (/), multiply (*) and additionally the pct function which turns the number into a percent (dividing by 100).

The unary functions are exponential (e^x), power of two (2^x), power of 10 (10^x), natural log (ln), sin, cos, tan, log of 2, invert (1 / x), square root (√), cubed root (x^(1/3)), negate (* -1).

The other functions do not contribute to flow of state in the application.

All internal calculations are performed using curied partial functions. The principle difference between binary and unary operations is unary operations are applied to the answer slot alone and are not impacted by the entry value.

Equal

The equal function operates similarly to standard desktop calculators, applying the curried function repetedly on the prior result on each call to the equal function.

Constants

There's also four mathematical constants, e, pi, phi, and sqrt(2) (pythagoean constant). Calling a constant will replace the current entry value. Random numbers can be generated using the rand function, this also replaces the current entry value. There's a simple memory system with two variables, v1 and v2. Each has a set and recall function that pulls from the answer and recalls to the entry value.

Clearing

Finally there are clear functions, C and CE. CE clears the current entry and C clears all internal state.

Properties

There are several read only properties, entry, answer, v1, v2, which gives access to the respective private properties.

Basic Program Flow

Entering a Number

After constructing or hard clearing a StateCalc you must enter a number before you can perform any futher operations. You have several choices for how to enter a number, you can use one of the 4 constants, e, pi, phi or the pythagorean constant. Additionally, you can generate a random number between 0 and 1.

You can add a number directly using the addNumber function. Numbers are entered sequentially, just like in a desktop calculator. Float numbers can be entered using the decimalFunction, which will only execute once for any operand preventing the creation of non-numbers.

Calling Functions

Unary Function

After a number is entered and equal set to place it into the answer slot, you can use any of the unary functions listed above and a result will be available on the answer property.

Binary Functions

After calling a binary function you must either add another number, or call equal. Calling equal before adding another number will apply the function to the previous entry. If equal is called after entering a another number then the function is applied to the current and previous entry. Aftering calling equal the result will be available on the answer property.

API

properties

entry

A read only property that gives the current entry to the calculator, attempting to set the property will simply return the previous value.

answer

A read only property that gives the current answer, attempting to set the property will simply return the previous value.

v1

A read only property that gives the current number stored in variable 1 to, attempting to set the property will simply return the previous value.

v2

A read only property that gives the current number stored in variable 1 to, attempting to set the property will simply return the previous value.

methods

addNumber

The add number function takes an interger (will floor floats) and adds it to the current entry. This was intended to add digits sequentially like a calculator, but it is possible to enter the entire integer or decimal portion at once.

For example the following are equivalent:

calc.addNumber(100);
calc.addDecimal();
calc.addNumber(123);
console.log(calc.entry) // "100.123"

calc.addNumber(1);
calc.addNumber(0);
calc.addNumber(0);
calc.addDecimal();
calc.addNumber(1);
calc.addNumber(2);
calc.addNumber(3);
console.log(calc.entry) // "100.123"

addDecimal

Adds a decimal to the current entered number, will not allow multiple decimals to be added to the same number.

calc.addNumber(1);
calc.addDecimal();
calc.addNumber(1);
console.log(calc.entry) // 1.1
calc.addNumber(1);
calc.addDecimal();
calc.addNumber(1);
console.log(calc.entry) // 1.11

negate

Negates the current entry.

calc.addNumber(1);
console.log(calc.entry) // 1
calc.negate()
console.log(calc.entry) // -1

pct

Turns the current entry into a percent (divides by 100).

calc.addNumber(1);
console.log(calc.entry) // 1
calc.pct()
console.log(calc.entry) // .01
calc.pct()
console.log(calc.entry) // .0001

rand

Generates a random number between 0 and 1 and stores it in the entry.

calc.rand();
console.log(calc.entry) // random

c

Will clear all internal state

calc.addNumber(1);
calc.equal();

console.log(calc.entry); // 1
console.log(calc.answer); // 1

calc.c();
console.log(calc.entry); // 0
console.log(calc.answer); // 0

ce

Will clear current entry.

calc.addNumber(1);
calc.equal();

console.log(calc.entry); // 1
console.log(calc.answer); // 1

calc.ce();
console.log(calc.entry); // 0
console.log(calc.answer); // 1

setv1

Takes current answer and saves it in variable 1.

calc.addNumber(1);
calc.equal();
calc.setv1();
console.log(calc.v1);

setv2

Takes current answer and saves it in variable 2.

calc.addNumber(1);
calc.equal();
calc.setv2();
console.log(calc.v2);

recv1

Takes variable one and recalls it, replacing current entry.

calc.addNumber(1);
calc.equal();
calc.setv1();
console.log(calc.v1);
calc.ce();
console.log(calc.entry);
calc.recv1();
console.log(calc.entry);

equal

The equal operates differently depending on the current state of the calculator. If no number is entered, equal doesn't do anything. If a number is entered and no function is selected, equal transfers the value of the current entry to the answer. If a number is entered and a unary function is selected, equal is automatically called internally. If a number is entered and a binary function is selected, equal needs to be called manually after an additional number is entered. Calling equal multiples times in a row re-applies the previous function. Reapplications are always applied to the last parameter. If a number is entered and a binary function is selected and equal is called without adding an additional number, the function is applied using the current entry as both operands.

calc.addNumber(1);
calc.equal();
console.log(calc.entry);  // 1
console.log(calc.answer); // 1

func

The func method allows us to select a function using a string object. Every function that can be accessed using the func has also been dynamically applied to the object itself. That is, calling calc.func("plus") or calc.plus() gives the same result. The available functions are:

Unary Operations

• exp (exponential)
• pw2 (power of two)
• pw10 (power of ten)
• ln (natural log)
• sin (sin)
• cos (cos)
• tan (tan)
• sqrt (square root)
• qrt (cubed root)
• log (log base 2)
• vert (1/x)

Binary Operations

• plus (+, addition)
• minus (-, subtraction)
• div (/, division)
• mult (*, mult)

addNumber("2", stateCalc);
stateCalc.func("plus");
addNumber("2", stateCalc);
stateCalc.equal();
console.log(stateCalc.answer); // 4

dynamically added functions

As stated in the func section, all internal math functions can be called using their name as a method on StateCalc. That is, every method from exp to mult is also available as a method directly on the calculator object, with the same name as would be passed to the func method. hat is, calling calc.func("plus") or calc.plus() gives the same result.

addNumber("2", stateCalc);
stateCalc.plus();
addNumber("2", stateCalc);
stateCalc.equal();
console.log(stateCalc.answer); // 4

constants

e

Eulers constant.

calc.e();
console.log(calc.answer); // e

pi

Ratio of a circle's circumference to it's diameter.

calc.pi();
console.log(calc.answer); // pi

phi

The Golden Ratio

calc.phi();
console.log(calc.answer); // phi

py

The square root of 2, or the pythagorean constant.

calc.py();
console.log(calc.answer); // py

Scripts

Testing

To run mocha/chai tests. npm run test

Examples

To run the main example. npm run ex

To run all examples. npm run exAll

License

StateCalc.js is released under the MIT license.