Kap

Kap is an array-based language that aims to implement most of standard APL, along with additional features. Much of standard APL works in Kap, although if an APL feature does not fit with Kap's design, those features are changed or removed.

Lazy evaluation
The main difference compared to APL is that Kap is lazy-evaluated. This means that the language gives the developers very loose guarantees when (or if, and how many times) a function will actually be invoked. For example,  will only make a single call to   because   will not immediately evaluate the result but only return a delayed evaluation. Since all but the first result is then discarded, those results will never be computed.

Differences from APL
The following is a list of significant differences compared to APL:


 * Lazy evaluation
 * First class functions
 * Bignum support and rational arithmetic
 * Ability to define custom syntax
 * Native hash table support
 * Parallel evaluation (to take advantage of multi-core CPU's)