[Bug-apl] inner product -.= bug

[David Tran]

Hi,

      a ← 2 3 5 6
      b ← 4 5 5 6

      a -.= b

¯2   ⍝  bug? the value should be zero

      -/a=b
0

Version info:
~ $ apl --version
BUILDTAG:
---------
    Project:        GNU APL
    Version / SVN:  1.7 / Unversioned directory
    Build Date:     2017-10-05 09:52:49 UTC
    Build OS:       Darwin 17.0.0 x86_64
    config.status:  unknown configure options
   Archive SVN: 

Thanks,

David