npm install --save @thk2b/algebra
A javascript algebra engine
import { calculate, simplify } from 'algebra'
calculate('1+1') // => 2
calculate('2*2') // => 4
calculate('2(2+2)') // => 8, with implicit multiplication
calculate('5(10^2)(12-9)') // => 1500
calculate('10:sqrt(25)') // => 50
simplify('16/24') // => '2/3'Suported binary operators are +, -, *, /.
Unary operators must be preceded by the : character.
Suported unary operators are :sqrt, :sin, :cos, :tan.
The ultimate goal of this project is to parse and simplify algebraic expressions.
The output should be correct with regards to the rules of algebra. For instance, the order of operations must be respected.
Errors in invalid input strings should be identified and clearly communicated to the user.
-
Why not use
eval?Similar beahviour could be achieved by simply using
eval. But that would prevent implementing more complex behaviours, such as implicit multiplication,fraction reducing, algebraic variables, as well as custom operators such as exponentiation with the '^' sign.
The code is written in a functional style. A previous imperative version of the code is available unser the imperative branch, though the algorithm is the same.
There are two core modules:
The lexer, defined in src/core/lex/, takes an input string and returns a list of tokens.
It identifies numbers, operands, and parentheses.
It also handles token transformation based on context. For instance, it differentiates negative numbers from substractions, and handles implicit multiplication (ie 2(2+10) is interpreted as 2*(2+10)).
The parser, defined in src/core/parse/, takes a list of tokens and produces a syntax tree.
It handles operation precedence, and parentheses.
Then, higher level functions, such as calculate, reduce or solve are defined on the parse tree. These are public facing functions that use the core internally.