@atomic-ehr/fhirpath/src/operations/div-operator.ts

A TypeScript implementation of FHIRPath

import type { OperatorDefinition } from '../types';
import { PRECEDENCE } from '../types';
import type { OperationEvaluator } from '../types';
import { box, unbox } from '../boxing';

export const evaluate: OperationEvaluator = async (input, context, left, right) => {
  if (left.length === 0 || right.length === 0) {
    return { value: [], context };
  }
  
  const boxedLeft = left[0];
  const boxedRight = right[0];
  if (!boxedLeft || !boxedRight) {
    return { value: [], context };
  }
  
  const leftValue = unbox(boxedLeft);
  const rightValue = unbox(boxedRight);
  
  if (rightValue === 0) {
    return { value: [], context };
  }
  
  const result = Math.floor((leftValue as any) / (rightValue as any));
  return { value: [box(result, { type: 'Integer', singleton: true })], context };
};

export const divOperator: OperatorDefinition & { evaluate: OperationEvaluator } = {
  symbol: 'div',
  name: 'div',
  category: ['arithmetic'],
  precedence: PRECEDENCE.MULTIPLICATIVE,
  associativity: 'left',
  description: 'Performs truncated division (integer division) of the left operand by the right operand, ignoring any remainder. Always returns an Integer, even if operands are Decimal. Division by zero returns empty.',
  examples: ['5 div 2', '5.5 div 0.7', '10 div 3', '5 div 0'],
  signatures: [
    {
      name: 'integer-div',
      left: { type: 'Integer', singleton: true },
      right: { type: 'Integer', singleton: true },
      result: { type: 'Integer', singleton: true },
    },
    {
      name: 'decimal-div',
      left: { type: 'Decimal', singleton: true },
      right: { type: 'Decimal', singleton: true },
      result: { type: 'Integer', singleton: true },
    }
  ],
  evaluate
};