The MATIOTA Function

The MATIOTA function (aka ROWFIND) is an assembler-based FastFn that performs character matrix lookup in a manner analogous to the {iota} function. The file contains the latest version of this program for the APL*PLUS II/386 and III/Windows systems, including performance enhancements and bug fixes. On +III, load the workspace using )LOAD MATIOTA.WS and read DESCRIBE for conversion instructions.

If you want to use MATIOTA on a different APL system, you're on your own. I'm afraid I don't currently have time to port it to other APLs. But here is the source code to get you started:

If you use my code as the basis for an adaptation, I'd appreciate a credit line in your code. If your version is available on the Net, send me the URL ( and I'll be happy to add a link to your site.

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