Arrays in Forth
Hacker News
February 15, 2026
AI-Generated Deep Dive Summary
Arrays in Forth: A Flexible Approach
For those new to Forth, the absence of standard features like arrays can seem confusing. However, this language’s unique strength lies in its ability to create custom data types tailored to specific needs, making pre-defined structures unnecessary. Forth users often invent solutions that perfectly fit their programs rather than forcing them into arbitrary standards.
The article distinguishes between two main array types: unindexed and indexed. Unindexed arrays allocate a fixed number of bytes at compile-time and return the origin address at runtime—essentially functioning as work areas or buffers. Indexed arrays, on the other hand, treat memory as divided into equal-sized elements. These can be variable-like (returning addresses), value-like (holding values), or even execution vectors (storing actions). The most common indexed array in Forth is a simple 1D structure with single-cell elements.
The flexibility of Forth’s arrays becomes evident when addressing complex data needs, such as in the Game 0 example. Here, each room requires five cells for data storage—a task that standard arrays cannot handle due to their fixed element size limitation. The article introduces *long-element-array*, a defining word that allows variable-length elements, making it ideal for projects with diverse data requirements.
For tech enthusiasts and developers, Forth’s approach to arrays offers valuable insights into the power of language flexibility. By enabling users to define custom data structures, Forth demonstrates how programming can prioritize adaptability over rigid standards—a lesson that resonates with anyone seeking efficient, tailored solutions in their work.
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Originally published on Hacker News on 2/15/2026