Implement TEXTBEFORE function

[Jython1415]

Overview

Implement the TEXTBEFORE function for the named-functions library.

Description

Returns text that occurs before a given character or string.

Value Proposition

• Pairs with TEXTAFTER for comprehensive text parsing capabilities
• Useful for extracting prefixes and everything before a delimiter
• Common pattern in data cleaning and text processing workflows

Priority

HIGH

Category

Text Manipulation

Implementation Notes

• Should handle cases where delimiter is not found
• Consider parameter for instance number (e.g., 2nd occurrence)
• Consider parameter for match mode (case-sensitive/insensitive)
• Should handle edge cases like empty strings
• API should mirror TEXTAFTER for consistency

Related

Part of Excel function implementation initiative (#51)

[Jython1415]

Implemented in #124