Eigen function in as it used to be in old versions of Dyalog APL

Eigen.dyalog

 Eigen←{⎕IO ⎕ML←1                             ⍝ Eigen values⍪vectors
                                             ⍝ graeme@dyadic.com
     dsyev←{                                 ⍝ real symmetric:
         args←'dsyev_'assoc↓⍉↑⌽{             ⍝ associate external fn.
             ⍵,⊂' <T1 ' 'V'}{                ⍝ JOBZ
             ⍵,⊂' <T1 ' 'L'}{                ⍝ UPLO
             ⍵,⊂' <I4 'n}{                   ⍝ N
             ⍵,⊂' =F8[] '(,mat)}{            ⍝ A
             ⍵,⊂' <I4 'n}{                   ⍝ LDA
             ⍵,⊂' >F8[] 'n}{                 ⍝ W
             ⍵,⊂' >F8[] '(¯1+3×n)}{          ⍝ WORK
             ⍵,⊂' <I4 '(¯1+3×n)}{            ⍝ LWORK
             ⍵,⊂' >I4  ' 0}⍬                 ⍝ INFO

         vecs vals _ code←dsyev_ args        ⍝ call external fn.
         code=0:vals join vecs               ⍝ good rslt: values⍪vectors.
         ⎕SIGNAL 11                          ⍝ else: DOMAIN ERROR.
     }

     dgeev←{                                 ⍝ real general:
         args←'dgeev_'assoc↓⍉↑⌽{             ⍝ associate external fn.
             ⍵,⊂' <C1 ' 'N'}{                ⍝ JOBVL
             ⍵,⊂' <C1 ' 'V'}{                ⍝ JOBVR
             ⍵,⊂' <I4 'n}{                   ⍝ N
             ⍵,⊂' =F8[] '(,⍉mat)}{           ⍝ A
             ⍵,⊂' <I4 'n}{                   ⍝ LDA
             ⍵,⊂' >F8[] 'n}{                 ⍝ WR
             ⍵,⊂' >F8[] 'n}{                 ⍝ WI
             ⍵,⊂' >I4 ' 0}{                  ⍝ VL
             ⍵,⊂' <I4 ' 1}{                  ⍝ LDVL
             ⍵,⊂' >F8[] '(n×n)}{             ⍝ VR
             ⍵,⊂' <I4 'n}{                   ⍝ LDVR
             ⍵,⊂' >F8[] '(4×n)}{             ⍝ WORK
             ⍵,⊂' <I4 '(4×n)}{               ⍝ LWORK
             ⍵,⊂' >I4 ' 0}⍬                  ⍝ INFO

         _ vals cmpx _ vecs _ code←dgeev_ args   ⍝ call external fn.
         code≠0:⎕SIGNAL 11                   ⍝ DOMAIN ERROR.
         0∧.=cmpx:vals join vecs             ⍝ real
         VR←⍉n n⍴vecs
         Ei←vals,¨cmpx
         Eii←VR×[2]cmpx=0
         WI←cmpx,0                           ⍝ {(⍵≠0)^⍵=-1⌽⍵}WI,0
         pair←(WI≠0)∧WI=-1⌽WI                ⍝ problem if 3 same in a row!
         pair←pair/⍳⍴pair
         Eii[;pair]←VR[;pair],¨VR[;1+pair]
         Eii[;1+pair]←VR[;pair],¨-VR[;1+pair]
         Ei⍪Eii
     }

     zheev←{                                 ⍝ complex hermitian:
         args←'zheev_'assoc↓⍉↑⌽{             ⍝ associate external fn.
             ⍵,⊂' <C1   ' 'V'}{              ⍝ JOBZ
             ⍵,⊂' <C1   ' 'L'}{              ⍝ UPLO
             ⍵,⊂' <I4   'n}{                 ⍝ N
             ⍵,⊂' =F8[] '(∊⍉mat)}{           ⍝ A
             ⍵,⊂' <I4   'n}{                 ⍝ LDA
             ⍵,⊂' >F8[] 'n}{                 ⍝ W
             ⍵,⊂' >F8[] '(¯2+4×n)}{          ⍝ WORK
             ⍵,⊂' <I4   '(¯1+2×n)}{          ⍝ LWORK
             ⍵,⊂' >F8[] '(¯2+3×n)}{          ⍝ RWORK
             ⍵,⊂' >I4   ' 0}⍬                ⍝ INFO

         vecs vals _ _ code←zheev_ args      ⍝ call external fn.
         code=0:vals join cmpx vecs          ⍝ good rslt: values⍪vectors.
         ⎕SIGNAL 11                          ⍝ else: DOMAIN ERROR.
     }

     zgeev←{                                 ⍝ complex general:
         args←'zgeev_'assoc↓⍉↑⌽{             ⍝ associate external fn.
             ⍵,⊂' <C1   ' 'N'}{              ⍝ JOBVL
             ⍵,⊂' <C1   ' 'V'}{              ⍝ JOBVR
             ⍵,⊂' <I4   'n}{                 ⍝ N
             ⍵,⊂' =F8[] '(∊⍉mat)}{           ⍝ A
             ⍵,⊂' <I4   'n}{                 ⍝ LDA
             ⍵,⊂' >F8[] '(2×n)}{             ⍝ W
             ⍵,⊂' <I4   ' 0}{                ⍝ VL
             ⍵,⊂' <I4   ' 1}{                ⍝ LDVL
             ⍵,⊂' >F8[] '(2×n×n)}{           ⍝ VR
             ⍵,⊂' <I4   'n}{                 ⍝ LDVR
             ⍵,⊂' >F8[] '(4×n)}{             ⍝ WORK
             ⍵,⊂' <I4   '(2×n)}{             ⍝ LWORK
             ⍵,⊂' >F8[] '(2×n)}{             ⍝ RWORK
             ⍵,⊂' >I4   ' 0}⍬                ⍝ INFO

         _ vals vecs _ _ code←zgeev_ args    ⍝ call external fn.
         code=0:(cmpx vals)join cmpx vecs    ⍝ good rslt: values⍪vectors.
         ⎕SIGNAL 11                          ⍝ else: DOMAIN ERROR.
     }

     assoc←{                                 ⍝ associate external function.
         types args←⍵                        ⍝ argument types and values.
         3=⎕NC ⍺:args                        ⍝ function already exists.
         {args}⎕NA'lapack|',⍺,∊types         ⍝ associate external function.
     }

     fuzz←{                                  ⍝ fuzzy comparison.
         ⎕CT←2*¯32                           ⍝ coarse tolerance for max fuzz.
         noise←(○1)+*1                       ⍝ offset for comparison.
         (⍺+noise)⍺⍺ ⍵+noise                 ⍝ tolerant comparison.
     }

     join←{⍺⍪⍉n n⍴⍵}                         ⍝ join real vals and vecs.
     cmpx←{↓(0.5×⊃⍴⍵)2⍴⍵}                    ⍝ complex from real.

     n←⊃⍴mat←⍵                               ⍝ matrix size and content.

     1=≡⍵:{                                  ⍝ real matrix.
         (⍵≡fuzz⍉⍵)∧2≠⊃⍴⍵:dsyev ⍵            ⍝ symmetric (not 2×2).
         dgeev ⍵                             ⍝ non-symmetric.
     }⍵
                                             ⍝ complex matrix.
     ⍵≡fuzz⍉⍵×⊂1 ¯1:zheev ⍵                  ⍝ hermitian:
     zgeev ⍵                                 ⍝ non-hermitian.
 }