Dyalog is the most popular implementation; It's alive and kicking, can do COM and .NET on windows. Dyalog is closed source and proprietary.
There's also J http://jsoftware.com which is the APL's designer "fix all the deficiencies" iteration. It only uses ASCII characters, and takes APL to the extreme -- e.g., +/ % # (that is: plus-slash-percent-hash) is a complete unary function that computes averages. J is open source.
And there's also K, http://kx.com which is popular in the financial world. The relation is K:J like C:Ada, I think. Whereas J strives to be pure, and mathematically complete and extremely well defined and rounded, K throws away almost every language redundancy (e.g. it only has nested vectors, which are also used to represent matrices), and does everything to be superfast. In the latest revision of the language, K4, they incorporate a database into the language. There's an open source implementation of K3 called Kona which you can find on github.
There's also J http://jsoftware.com which is the APL's designer "fix all the deficiencies" iteration. It only uses ASCII characters, and takes APL to the extreme -- e.g., +/ % # (that is: plus-slash-percent-hash) is a complete unary function that computes averages. J is open source.
And there's also K, http://kx.com which is popular in the financial world. The relation is K:J like C:Ada, I think. Whereas J strives to be pure, and mathematically complete and extremely well defined and rounded, K throws away almost every language redundancy (e.g. it only has nested vectors, which are also used to represent matrices), and does everything to be superfast. In the latest revision of the language, K4, they incorporate a database into the language. There's an open source implementation of K3 called Kona which you can find on github.