easy-path-expressions

Easy Path Expressions

Easy-path-expressions is a syntax parser that converts basic mathematical expressions into FHIRPath notation.

Local Installation

npm install

To test that easy-path-expressions is working correctly:

npm test

Usage

import * as easyPathExpressions from 'easy-path-expressions';
easyPathExpressions.fhirConvert("(a+b)^2", ["a", "b"]); // returns ($a+$b).power(2)
easyPathExpressions.fhirConvert("CEILING(a*b)", ["a", "b"]); // returns ($a*$b).ceiling()

fhirConvert is the main function of easy-path-expressions, which validates and converts an inputted expression to fhirpath. fhirConvert will also return null if the expression fails validation.

fhirConvert takes in two inputs: the mathematical expression for conversion and an array of usable variables. The format is as follows:

fhirConvert([expression], [vars])

Basic syntax expressions utilize traditional operators and function statements. Expressions can be written using variable names, mathematical operators, and various functions. The syntax guide is bellow.

Syntax Guide

USABLE OPERATORS: +, -, *, /, ^, **, !=, !~, >=, <=, =, &&, ||, xor, and, or, implies

USABLE FUNCTIONS: CEILING(), FLOOR(), ABS(), LOG(), TRUNCATE(), EXP(), SQRT(), LN(), NOT(), LENGTH()

• Usage: CEILING([expression]), FLOOR([expression]), etc.

LOG()

• Usage: LOG([Base], [Value])

USABLE VARIABLES: Any string of letters and numbers differing from the aforementioned functions.

EXAMPLE EXPRESSIONS (vars: [a, b, c]): 2+2 (a+b)^3 CEILING(LOG(2, 17)) TRUNCATE(ABS(-3.3)) + SQRT(LN(a+b+c))

EXAMPLE OUTPUTS:

INPUT: fhirConvert("2+2", ["a", "b", "c", "d"]) OUTPUT: "2+2"

INPUT: fhirConvert("(a+b)^3", ["a", "b", "c", "d"]) OUTPUT: "((%a+%b).power(3))"

INPUT: fhirConvert("CEILING(LOG(2, 17))", ["a", "b", "c", "d"]) OUTPUT: "((17.log(2)).ceiling())"

INPUT: fhirConvert("TRUNCATE(ABS(-3.3))+SQRT(LN(a+b+c))", ["a", "b", "c", "d"]) OUTPUT: "((-3.3).abs()).truncate()+((%a+%b+%c).ln()).sqrt()"