support for APL character overstrikes in en_US.UTF-8/Compose

Geoff Streeter geoff at
Tue Jan 3 07:28:20 PST 2012

I have proposed some additional compositions to support the APL programming language. See

APL started with IBM golf ball terminals and has always had the concept of composed characters which were built with overstrikes. So ∇ overstruck | produced ⍒.

The additions proposed cover all of the overstrikes which can be produced by the variants of apl keyboards in xkb/sybols/apl which has just been updated by Sergey.

I have also provided support for the circled alphabet and the circled digits. Since the letter "o" had already been used with "c" and "r" for the copyright  and registered symbols, I used the digit "0". I also coded the use of the "○". I have only coded these in one order the "0" or "○" have to come first.

For the actual APL characters I have coded both orders.

I could have worked my way through the whole "Mathematical Operators" and "Miscellaneous Technical" but I am not aware of the cost of an extra line in "Compose". I have only coded the characters that I am aware of being in use in extant APLs.

Is en_US.UTF-8/Compose.pre the only file I should be changing? Should I be creating an "apl" locale with its own Compose file that is then included in en_US.UTF-8/Compose?

Geoff Streeter

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