Fix LOOKUP function to find nearest match

[stanim]

PR Details

Fix LOOKUP function to find nearest match

Description

The LOOKUP function should return the nearest match:

If the LOOKUP function can't find the lookup_value, the function matches the largest value in lookup_vector that is less than or equal to lookup_value.

If lookup_value is smaller than the smallest value in lookup_vector, LOOKUP returns the #N/A error value.

Important: The values in array must be placed in ascending order: ..., -2, -1, 0, 1, 2, ..., A-Z, FALSE, TRUE; otherwise, LOOKUP might not return the correct value. Uppercase and lowercase text are equivalent.

According to the official Microsoft Excel documentation: https://support.microsoft.com/en-us/office/lookup-function-446d94af-663b-451d-8251-369d5e3864cb

Related Issue

Fixes #997

Motivation and Context

This helps with Excels from third party, where one has no control which form of LOOKUP is used.

How Has This Been Tested

Added tests to calc_test.go

Tested on:

• OS: Archlinux 5.13.10-arch1-1
• WPS Spreadsheets (version wps-office 11.1.0.10702-1)
• LibreCalc (version libreoffice-fresh 7.1.5-2)

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[xuri]

LGTM, thanks for your PR.