# BQN runtime. Requires:
#   Type Fill Log GroupLen GroupOrd _fillBy_
#   !+-×÷⋆⌊=≤≢⥊⊑↕⌜`⊘
# Filled in by runtime: glyphs and default PrimInd
Decompose ← {0‿𝕩}
PrimInd ← {𝕩}
SetPrims ← {Decompose‿PrimInd ↩ 𝕩}

◶ ← {𝕨((𝕨𝔽𝕩)⊑𝕘){𝔽}𝕩}     # LIMITED to number left operand result
⊢ ← {𝕩}
⊣ ← {𝕩}⊘{𝕨}
˙ ← {𝕩⋄𝕗}
˜ ← {𝕩𝔽𝕨⊣𝕩}
∘ ← {𝔽𝕨𝔾𝕩}
○ ← {(𝔾𝕨)𝔽𝔾𝕩}
⊸ ← {(𝔽𝕨⊣𝕩)𝔾𝕩}
⟜ ← {(𝕨⊣𝕩)𝔽𝔾𝕩}
⍟ ← {𝕨((𝕨𝔾𝕩)⊑⊢‿𝕗){𝔽}𝕩}   # LIMITED to boolean right operand result

IsArray←0=Type
Int←(1=Type)◶⟨0,⌊⊸=⟩
Nat←(1=Type)◶⟨0,0⊸≤×⌊⊸=⟩
Deshape←IsArray◶{𝕩Fill⟨𝕩⟩}‿⥊
Pair ← {⟨𝕩⟩} ⊘ {⟨𝕨,𝕩⟩}
Box ← {𝕩Fill⟨⟩⥊⟨𝕩⟩}
ToArray ← Box⍟(1-IsArray)

# LIMITED to numeric arguments for arithmetic cases
≥ ←            ≤˜
< ← Box      ⊘ (1-≥)
> ←            (1-≤)
⌊ ↩ ⌊        ⊘ (>⊑{𝕨‿𝕩})
⌈ ← -∘⌊∘-    ⊘ (<⊑{𝕨‿𝕩})
| ← 0⊸≤◶-‿⊢
≠ ← (0<=)◶⟨1⋄0⊑≢⟩  # LIMITED to monadic case

_fold←{
  "´: 𝕩 must be a list" ! 1==𝕩
  l←≠v←𝕩 ⋄ F←𝔽
  r←𝕨 (0<l)◶{𝕩⋄Identity f}‿{l↩l-1⋄l⊑𝕩}⊘⊣ 𝕩
  {r↩(𝕩⊑v)F r}⌜(l-1)⊸-⌜↕l
  r
}
´ ← _fold

_qSearch ← {+´·×`𝕗(1-=)⌜<}
_glyphLookup_ ← {
  {PrimInd𝕩} ⊑ ((𝕘⊑˜𝕗_qSearch)⌜glyphs)˙
}
_isGlyph ← { (glyphs _qSearch 𝕗) = {PrimInd𝕩} }
IsJoin ← '∾'_isGlyph

Cell←{(𝕨⊸+⊑𝕩˙)⌜↕(≠𝕩)-𝕨}⟜≢

∾ ← {k←≠𝕨⋄k⊸≤◶⟨⊑⟜𝕨⋄-⟜k⊑𝕩˜⟩⌜↕k+≠𝕩}  # LIMITED to two vector arguments

GetCells←(1==∘⊢)◶{
  c←1×´s←1 Cell 𝕩
  𝕨((⥊𝕩)⊑˜c⊸×⊸+)⌜s⥊↕c
}‿{
  ⊑⟜𝕩⌜𝕨
} _fillBy_ ⊢
⊏ ← GetCells  # LIMITED to depth-1 natural number left argument

_eachd←{
  _d←{ # Equal ranks
    p←≢𝕨
    "Mapping: Equal-rank argument shapes don't agree" ! 1(⊑⟜p=⊑⟜(≢𝕩))⊸×´↕=𝕨
    p⥊ (⊑⟜(⥊𝕨)𝔽⊑⟜(⥊𝕩))⌜↕1×´p
  }
  _e←{ # 𝕨 has smaller or equal rank
    p←≢𝕨 ⋄ k←=𝕨 ⋄ q←≢𝕩
    "Mapping: Argument shape prefixes don't agree" ! 1(⊑⟜p=⊑⟜q)⊸×´↕k
    l←1(q⊑˜k⊸+)⊸×´↕(=𝕩)-k
    a←⥊𝕨 ⋄ b←⥊𝕩
    q⥊⥊(≠a) (⊑⟜a𝔽l⊸×⊸+⊑b˙)⌜○↕ l
  }
  =○=◶⟨>○=◶⟨𝔽_e⋄𝔽˜_e˜⟩⋄𝔽_d⟩
}

_perv←{ # Pervasion
  R←𝔽{𝕨𝔽_perv𝕩}
  +○IsArray◶⟨
    𝔽
    R⌜⊘(>○IsArray◶{𝕨{𝕗R𝕩}⌜𝕩}‿{𝕩{𝕩R𝕗}⌜𝕨}) _fillBy_ R
    R _eachd _fillBy_ R
  ⟩
}

Cmp0 ← ≥-≤
Cmp1 ← (0<1×´≢∘⊢)◶⟨1, IsArray∘⊢◶(1-2×≤)‿{𝕨Cmp1𝕩}⟜(0⊑⥊)⟩
Cmp ← +○IsArray◶⟨
  Cmp0
  IsArray∘⊣◶⟨Cmp1,-Cmp1˜⟩
  {
    lc←𝕨CmpLen○≢𝕩
    cc ← (⊑⟜(⥊𝕨))⊸Cmp⟜(⊑⟜(⥊𝕩)) _getCellCmp´ lc
    Cc˜0
  }
⟩
_grade_←{
  "⍋𝕩: 𝕩 must have rank at least 1" ! 1≤=𝕩
  l←≠𝕩
  m←1×´1 Cell 𝕩
  d←⥊𝕩
  # Counting sort for small-range ints
  bl←bu←0⋄r←1-{((bu↩⌈´𝕩)-bl↩⌊´𝕩)≤2×l}⟜𝕩⍟⊢((m=1)×32<l)◶0‿(1×´Int⌜)d
  0 Fill r◶⟨GroupLen⊸GroupOrd (𝕘⊑⟨-⟜bl,bu⊸-⟩)⌜ ⋄ 𝔽{𝕩⋄
    # Merge sort
    GT←(m 𝔽○(⊑⟜d) _getCellCmp 0)>0˜
    B←l⊸≤◶⊢‿l
    (↕l){
      i←-d←𝕨 ⋄ j←ei←ej←0
      e←3 ⋄ G←GT○(⊑⟜(m⊸×⌜⍟(1-m=1)𝕩)) ⋄ c←⟨G,0,1,2⟩
      s←(8≤d)⊑⟨+,{(𝕩-1){𝕩⋄e↩2⋄j↩i⋄i↩𝕩}⍟(1-G)⍟(1-e)𝕩}⟩
      N←{i↩d+𝕨⋄ej↩B d+ei↩B j↩d+𝕩⋄e↩l≤j⋄S ei⋄i R j}
      R←{𝕨e◶c𝕩}◶{e+↩2×ei=i↩1+𝕨⋄𝕨}‿{e+↩ej=j↩1+𝕩⋄𝕩}‿N
      {(i R j)⊑𝕩}⟜𝕩⌜𝕩
    }´(2⋆ni-1+⊢)⌜↕ni←⌈2 Log l+l=0
  }⟩𝕩
}

Indices←{
  "/: Replication argument must have rank 1" ! 1==𝕩
  l←≠𝕩
  0 Fill {
    "/: Amounts to replicate must be natural numbers" ! 1×´Nat⌜𝕩
    k←l-1
    N ← ((⊢+-×0=𝕩⊑˜⊢)`k⊸-⌜↕l)⊑˜k-⊢  # Next nonzero
    E ← ⊑⟜(+`𝕩)
    ei←E i←N 0
    {{ei↩E i↩N𝕩+1⋄i}⍟(𝕩=ei)i}⌜↕E k
  }⍟(0<l)𝕩
}

Transpose←(0<=)◶⟨ToArray,{
  l←≠𝕩 ⋄ m←1×´c←1 Cell 𝕩
  (c⥊↕m)(+⟜(m⊸×)⊑(⥊𝕩)˙)⌜↕l
}_fillBy_⊢⟩
TransposeInv←{
  r←1-˜=𝕩 ⋄ s←≢𝕩 ⋄ l←r⊑s ⋄ c←⊑⟜s⌜↕r
  (↕l)(+⟜(l⊸×)⊑(⥊𝕩)˙)⌜c⥊↕1×´c
}_fillBy_⊢⍟{IX IsArray𝕩⋄0<=𝕩}

Reverse←{
  "⌽𝕩: 𝕩 must have rank at least 1" ! 1≤=𝕩
  l←≠𝕩
  ((l-1)⊸-⌜↕l) ⊏ 𝕩
}
Rot←{
  "𝕨⌽𝕩: 𝕨 must consist of integers" ! Int𝕨
  l←≠𝕩 ⋄ 𝕨-↩l×⌊𝕨÷l+l=0 ⋄ ((𝕨+⊢-l×(l-𝕨)≤⊢)⌜↕l) ⊏ 𝕩
}

Prefixes←{
  "↑𝕩: 𝕩 must have rank at least 1" ! 1≤=𝕩
  0⊸⊑⊸Fill ↕⊸⊏⟜𝕩⌜ ↕1+≠𝕩
}
Suffixes←{
  "↓𝕩: 𝕩 must have rank at least 1" ! 1≤=𝕩
  l←≠𝕩
  l⊸⊑⊸Fill {𝕩⊸+⌜↕l-𝕩}⊸⊏⟜𝕩⌜ ↕1+l
}

_sort ← {(𝕗⊑⟨Cmp,Cmp˜⟩)_grade_𝕗 ⊸ ⊏}

FirstCell←{
  "⊏𝕩: 𝕩 must have rank at least 1" ! 1≤=𝕩
  "⊏𝕩: 𝕩 cannot have length 0" ! 0<≠𝕩
  (<0) GetCells 𝕩
}
SelSub←{
  "𝕨⊏𝕩: 𝕨 must be an array" ! IsArray 𝕨
  "𝕨⊏𝕩: Indices in 𝕨 must be integers" ! 1×´⥊Int⌜ 𝕨
  l←≠𝕩
  "𝕨⊏𝕩: Indices out of range" ! 1×´⥊ ((-l)⊸≤×l⊸>)⌜ 𝕨
  𝕨 (⊢+l×0>⊢)⌜⊸⊏ 𝕩
}
First ← (0<≠)◶⟨Fill,0⊸⊑⟩ Deshape

IsPure ← {d←Decompose𝕩 ⋄ 2⊸≤◶⟨≤⟜0, 1(𝕊d⊑˜1⊸+)⊸×´·↕1-˜≠∘d⟩0⊑d}
_fillByPure_←{
  𝕘 (3≤Type∘⊣)◶⟨{𝕨Fill𝕏},{(𝕨HomFil𝕩)_fillBy_𝕨}⍟(IsPure⊣)⟩ 𝕗
}

¨ ↩ {𝕨𝔽⌜⊘(𝔽_eachd)_fillByPure_𝔽○ToArray𝕩}

StructErr←{𝕩}
IsStructErr ← (3=Type)◶⟨0,StructErr˙⊸=⟩
_under_←{
  val←𝕨𝔽○𝔾𝕩 ⋄ root‿ind←𝔾_structural 𝕩
  # Traverse indices 𝕩 and values 𝕨.
  # Return a list of index‿value pairs, or structErr if 𝕨 doesn't capture 𝕩.
  GetInserts←{
    conform ← {𝕨◶0‿𝕩}´⟨IsArray⊢, =○=, 1×´=¨○≢⟩
    Fail←{𝕊‿0}
    # 𝕎 is parent traversal; 𝕩 is current components of ind and val
    Trav←(IsArray 0⊑⊢)◶⟨Pair, Conform´∘⊢◶Fail‿{
      Parent←𝕎 ⋄ n←≠0⊑a←⥊¨𝕩 ⋄ j←¯1
      Child←Trav⟜(⊑¨⟜a)
      { j+↩1 ⋄ f←n⊸≤◶⟨𝕊˙⊸Child,Parent˙⟩j ⋄ F 0 }
    }⟩
    count←0⋄{IsArray◶⟨{𝕩⋄count+↩1},𝕊⌜⟩𝕩}𝕩
    next ← 0 Trav 𝕩‿𝕨
    res ← {n‿o←Next𝕩⋄next↩n⋄o}⌜ ↕count
    StructErr˙⍟(next=fail) res
  }⍟(1-IsStructErr∘⊢)
  Struct←{
    Set1←𝕨⊸{
      𝕩↩<⍟(1-IsArray)𝕩
      l←1×´s←≢𝕩
      i←0⊸⊑⌜𝕨
      g←Cmp0 _grade_ 0 i
      v←(1⊑⊑⟜𝕨)⌜g
      P←(≠g)⊸≤◶⟨(⊑⟜g)⊑i˙,l⟩
      e←P j←0
      s⥊{e=𝕩}◶⟨⊑⟜(⥊𝕩),{𝕩
        r←j⊑v⋄e↩{𝕊∘{𝕩
          "⌾: Incompatible result elements in structural Under"!r Match j⊑v
        }⍟(e=⊢)P j↩1+j}0⋄r
      }⟩⌜↕l
    }
    _at_ ← {(↕≠𝕩) 𝔽⍟((𝔾𝕩)=⊣)¨ 𝕩}
    Set ← 0⊸{ (𝕨≥≠root)◶⟨≢⥊(1+𝕨)⊸𝕊_at_(𝕨⊑root˙)∘⥊, Set1⟩ 𝕩 }
    IsArray∘root◶⟨1⊑0⊑𝕨˙, Set⟩ 𝕩
  } _fillBy_ ⊢
  IsStructErr◶⟨Struct⟜(𝕩˙), {𝕏val}·Inverse𝔾˙⟩ val GetInserts ind
}
Recompose ← ⊣◶⟨
  ⊢                  # 0 primitive
  ⊢                  # 1 block
  {𝕎𝕏}´⊢             # 2-train
  {F‿G‿H←𝕩⋄F G H}    # 3-train
  {F‿m←𝕩⋄F _m}       # 4 1-modifier
  {F‿m‿G←𝕩⋄F _m_ G}  # 5 2-modifier
⟩
_structural←{
  E←StructErr˙
  Inds ← IsArray◶⟨0,⥊⟜(↕1×´⊢)≢⟩ 𝕩 ⊑⟜⥊⍟(IsArray⊢)´ Reverse
  _s_ ← {
    f←𝕗
    st‿d‿o←𝕩
    g←𝕨 St Inds∘{f↩f(IsArray⊣)◶⟨⟩‿∾⟨𝕩⟩}⍟(d>IsArray) 𝕘
    {f _s_ 𝕩}⍟o g
  }
  IsStruct ← (5=0⊸⊑)◶⟨0,s˙=2⊸⊑⟩ Decompose
  _sfn ← {(IsStruct⊢)◶⟨𝕏, 𝕩‿𝕨‿𝕗{𝕨𝕏𝕗}⟩}
  Depth←1 _sfn ⋄ Info←0 _sfn

  Mon←{𝕏⊘E} ⋄ Dy←{E⊘𝕏}
  _errIf←{⊢⊘×○(1-𝔽)◶⟨E,𝕏⟩}
  SE ← IsStructErr _errIf⍟(3≥Type)
  NS ← IsStruct _errIf
  StructPrim ← ⊢ {𝕏𝕨} StructPrimClass ⊑ ⟨
    ⊢            # ⊢⊣˜∘○⊸⟜⊘◶
    Mon 1⊸Info   # =≠≢
    Mon 0⊸Depth  # <
    Mon 1⊸Depth  # ≍         # Dyad combines
    Dy  1⊸Depth  # ↕/»«⊔
        1⊸Depth  # ⥊↑↓⌽⍉⊏⊑
  # Mon 2⊸Depth  # >
  # Mon 2⊸Depth  # ∾         # Dyad combines
    (Type-3˙)◶⟨NS, {m←𝕩⋄{NS(𝕗_m)˙0}}, {m←𝕩⋄{NS(𝕗_m_𝕘)˙0}}⟩
  ⟩˙
  StructFn ← (0⊸⊑ 0⊸≤◶⟨3,2⊸≤◶⊢‿2⟩∘⊣◶⟨
    SE · StructPrim 0⊑⊢     #  0 primitive
    E˙                      #  1 block
    Recompose⟜{StructFn¨𝕩}  #    other operation
    SE 0⊑⊢                  # ¯1 constant
  ⟩ 1⊸Drop) Decompose
  IsStruct◶⟨0‿StructErr,1‿3⊏Decompose⟩ {𝕎𝕩}´ ⟨StructFn 𝕗, ¯1 _s_ 0⟩
}

match←{(0⊑𝕨)◶(1⊑𝕨)‿𝕩}´⟨
  ⟨=○IsArray, 0⟩
  ⟨IsArray∘⊢, =⟩
  ⟨=○=      , 0⟩
  ⟨1×´=¨○≢  , 0⟩
  {1×´⥊𝕨Match¨𝕩}
⟩
Depth←IsArray◶0‿{1+0(⊣-≤×-)´Depth⌜⥊𝕩}

≡ ← Depth          ⊘ Match
≢ ↩ IsArray◶⟨⟩‿≢   ⊘ (1-Match)

IF ← ⊢⊣!∘≡  # Intersect fill
IEF← (0<≠)◶⟨⊢_fillBy_ Fill, ⊢_fillBy_ IF´⟩∘⥊
_fillMerge_ ← {(0<≠∘⥊)◶⟨(𝔾○≢⥊⟨⟩˙)_fillBy_⊢⟜Fill, 𝔽 ⊣_fillBy_⊢ IEF⟩}
Merge←{
  c←≢0⊑⥊𝕩
  ">𝕩: Elements of 𝕩 must have matching shapes" ! 1×´(c≡≢)⌜⥊𝕩
  𝕩⊑⟜Deshape˜⌜c⥊↕1×´c
}_fillMerge_∾⍟IsArray

Join1←{
  # List of lists
  i←j←¯1 ⋄ e←⟨⟩ ⋄ a←𝕩
  {{e↩a⊑˜i↩𝕩⋄j↩¯1}⍟(1-i⊸=)𝕩⋄(j↩j+1)⊑e}⌜Indices≠⌜𝕩
}
JoinM←{
  # Multidimensional
  n←≠z←⥊𝕩 ⋄ s←≢⌜z ⋄ d←≠0⊑s ⋄ r←=𝕩
  "∾𝕩: Elements of 𝕩 must all have the same rank" ! 1×´(d=≠)⌜s
  "∾𝕩: 𝕩 element rank must be at least argument rank" ! d≥r
  _s0←{s←𝕨⋄F←𝔽⋄{o←s⋄s F↩𝕩⋄o}⌜𝕩}
  sh←≢𝕩 ⋄ p←1 ⋄ i←j←<0
  (Reverse 1×_s0 Reverse sh){
    q←𝕨
    a←𝕩⊑sh
    m←𝕩⊸⊑⌜s
    l←(q⊸×⊑m˙)⌜↕a
    "∾𝕩: 𝕩 element shapes must be compatible" ! 1×´m=¨⥊(↕p)⊢⌜l⊣⌜↕q
    k ← Indices l
    c ← -⟜(⊑⟜(k ⊏ 0+_s0 l))⌜ ↕≠k
    i ↩ (i ×⟜(⊑⟜l)⌜ k) +¨ i⊢⌜c
    j ↩ j ×⟜a⊸+⌜ k
    p×↩a
  }¨↕r
  G←(⥊⌜z){𝕨⊑𝕩⊑𝕗}¨
  i (r<d)◶G‿{
    Dr←((r⊸+)⌜↕d-r)⊸⊏
    t←Dr 0⊑s
    "∾𝕩: 𝕩 element trailing shapes must match" ! 1×´(×´t=¨Dr)⌜s
    ti←t⥊↕tp←×´t⋄(𝕨tp⊸×⊸+⌜ti)G𝕩⊣⌜ti
  } j
}
Join←(2⌊=)◶⟨
  Merge, (1×´(1==)⌜)◶JoinM‿Join1, JoinM
⟩_fillMerge_{
  r←≠𝕨 ⋄ d←≠𝕩
  "∾𝕩: empty 𝕩 fill rank must be at least argument rank" ! d≥r
  (r≤⊣)◶⟨⊑⟜𝕨⊸×,⊢⟩⟜(⊑⟜𝕩)⌜↕d
} ⊣ "∾𝕩: 𝕩 must be an array"!IsArray

_takeDrop←{
  ⟨gl,Noop,_inds⟩←𝕗
  pre ← "𝕨"∾gl∾"𝕩: 𝕨 must "
  ernk ← "have rank at most 1"
  eint ← "consist of integers"
  {
    ernk ! 1≥=𝕨
    𝕨 ↩ Deshape 𝕨
    eint ! 1×´Int⌜𝕨
    r ← ≠𝕨
    s ← r {(1⌜∘↕𝕨-≠𝕩)∾𝕩}⍟(>⟜≠) ≢𝕩
    _c ← { (×⟜𝕗⌜𝕨) +⌜ 𝕩 }
    i←<0 ⋄ k←1 ⋄ UIk←{ i (k×𝕨)_c↩ k ↕⊸(𝕨_c)⍟(1-=⟜1) 𝕩 ⋄ k↩1 ⋄ ≠𝕩 }
    doFil←0
    sh ← (⊑⟜s Noop◶{k×↩𝕨⋄𝕨}‿(⊣ UIk {𝕩⋄doFil↩1}_inds) ⊑⟜𝕨)⌜ ↕r
    (0<=i)◶(s⊸⥊)‿{
      sh ∾↩ t ← (s⊑˜r⊸+)⌜↕(≠s)-r
      {i 𝕩_c↩ ↕𝕩}⍟(1-1⊸=) k×´t
      Sel ← ⊑⟜(⥊𝕩)
      𝕩{Sel↩0⊸≤◶⟨(Fill𝕨)˙,Sel⟩}⍟⊢doFil
      Sel⌜ sh ⥊ i
    }_fillBy_⊢ ToArray 𝕩
  }
}
Take ← ⟨"↑" ⋄ 1-=⟜| ⋄ { 𝔽⍟(𝕨⊸<)a←|𝕩 ⋄ (0<𝕩)◶⟨¯∞⍟(<⟜0)⌜+⟜(𝕨+𝕩)⌜, ¯∞⍟(𝕨⊸≤)⌜⟩↕a }⟩_takeDrop
Drop ← ⟨"↓" ⋄ 1-0⊸= ⋄ { 𝔽 ⋄ 0⊸<◶⟨↕0⌈+,<∘⊢+⌜·↕0⌈-⟩ }⟩_takeDrop

ShiftCheck←{
  "« or »: 𝕩 must have rank at least 1" ! 1≤=𝕩
  d←𝕩-○=𝕨
  "« or »: 𝕨 must not have higher rank than 𝕩" ! 0≤d
  "« or »: Rank of 𝕨 must be at least rank of 𝕩 minus 1" ! 1≥d
  s←1 Cell 𝕩
  "« or »: 𝕨 must share 𝕩's major cell shape" ! 1×´(⊑⟜s=+⟜(1-d)⊑(≢𝕨)˙)⌜↕≠s
  1×´s
}
ShiftBefore←{
  c←𝕨 ShiftCheck 𝕩
  n←c×(𝕩≤○=⊢)◶1‿≠𝕨
  (≢𝕩)⥊n⊸≤◶⟨⊑⟜(Deshape𝕨),-⟜n⊑(⥊𝕩)˙⟩⌜↕c×≠𝕩
}
ShiftAfter←{
  c←𝕨 ShiftCheck 𝕩
  l←c×≠𝕩
  n←c×(𝕩≤○=⊢)◶1‿≠𝕨
  m←l-n
  (≢𝕩)⥊m⊸≤◶⟨+⟜n⊑(⥊𝕩)˙,-⟜m⊑(Deshape𝕨)˙⟩⌜↕l
}
FC←{ # Fill cell
  "« or »: 𝕩 must have rank at least 1" ! 1≤=𝕩
  (Fill 𝕩)⌜ ⥊⟜(↕1×´⊢) 1 Cell 𝕩
}

Windows←{
  "𝕨↕𝕩: 𝕨 must have rank at most 1" ! 1≥=𝕨
  r←≠𝕨↩Deshape 𝕨
  𝕨{
    "𝕨↕𝕩: Length of 𝕨 must be at most rank of 𝕩" ! r≤=𝕩
    "𝕨↕𝕩: 𝕨 must consist of natural numbers" ! ×´Nat⌜𝕨
    s←≢𝕩
    l←(1+⊑⟜s-⊑⟜𝕨)⌜↕r
    "𝕨↕𝕩: Window length 𝕨 must be at most axis length plus one" ! ×´0⊸≤⌜l
    k←1×´t←(r⊸+⌜↕s≠⊸-r)⊏s
    str ← Reverse ×`⟨k⟩∾{(s⊑˜𝕩⊸-)⌜↕𝕩}r-1
    ⊑⟜(⥊𝕩)⌜ k +⌜⟜(t⥊↕)˜⍟(1-=⟜1) l +⌜○(+⌜´str{𝕨⊸×⌜↕𝕩}¨⊢) 𝕨
  }_fillBy_⊢⍟(0<r)𝕩
}

˘ ← {𝕨 𝔽 _rankOp_ ¯1 𝕩}
_onAxes_←{
  F←𝔽
  (𝔾<≡)∘⊣◶{ # One axis
    "First-axis primitive: 𝕩 must have rank at least 1" ! 1≤=𝕩
    𝕨F𝕩
  }‿{ # Multiple axes
    "Multi-axis primitive: 𝕨 must have rank at most 1" ! 1≥=𝕨
    "Multi-axis primitive: Length of 𝕨 must be at most rank of 𝕩" ! 𝕨≤○≠≢𝕩
    l←≠𝕨 ⋄ W←⊑⟜(⥊𝕨)
    0{(W𝕨)F(1+𝕨)⊸𝕊˘⍟(𝕨<l-1)𝕩}⍟(0<l)𝕩
  }⟜ToArray
}

÷ ↩ ÷ _perv
⋆ ↩ ⋆ _perv
√ ← ⋆⟜(÷2)   ⊘ (⋆⟜÷˜)
| ← (|       ⊘ {𝕩-𝕨×⌊𝕩÷𝕨}) _perv
⌊ ↩ (⌊       ⊘ {(𝕨>𝕩)⊑𝕨‿𝕩}) _perv
⌈ ↩ (-∘⌊∘-   ⊘ {(𝕨<𝕩)⊑𝕨‿𝕩}) _perv
∧ ← 0 _sort  ⊘ (× _perv)
∨ ← 1 _sort  ⊘ ((+-×) _perv)
× ↩ (0⊸(<->) ⊘ ×) _perv
< ↩ Box      ⊘ ((1-≥) _perv)
> ↩ Merge    ⊘ ((1-≤) _perv)
≠ ↩ ≠        ⊘ ((1-=) _perv)
= ↩ =        ⊘ (= _perv)
≥ ← ("≥: No monadic form"!0˙) ⊘ (≥ _perv)
≤ ↩ ("≤: No monadic form"!0˙) ⊘ (≤ _perv)
+ ↩ + _perv
- ↩ - _perv
¬ ← 1+-
HomFil ← {((𝕎0) Fill 𝕏)⊘𝕏}⍟(+´⟨=,≠,≡,≢⟩=⊣)

ReshapeT ← "∘⌊⌽↑"_glyphLookup_(↕5)
Reshape←{
  "𝕨⥊𝕩: 𝕨 must have rank at most 1" ! 1≥=𝕨
  s←Deshape 𝕨
  sp←0+´p←¬Nat⌜s
  "𝕨⥊𝕩: 𝕨 must consist of natural numbers" ! 1≥sp
  n←≠d←Deshape 𝕩
  l←sp◶(1×´⊢)‿{
    lp←1×´p⊣◶⊢‿1¨𝕩
    "𝕨⥊𝕩: Can't compute axis length when rest of shape is empty" ! 0<lp
    i←0+´p×↕≠p
    t←ReshapeT i⊑s
    "𝕨⥊𝕩: 𝕨 must consist of natural numbers or ∘ ⌊ ⌽ ↑" ! t<4
    Chk ← ⊢ ⊣ "𝕨⥊𝕩: Shape must be exact when reshaping with ∘" ! ⌊⊸=
    a←(2⌊t)◶⟨Chk,⌊,⌈⟩n÷lp
    s↩p⊣◶⊢‿a¨s
    {d∾↩(Fill d)⌜↕𝕩-n⋄n}⍟(n⊸<)⍟(3=t)lp×a
  } s
  s⥊{
    𝕩(0<n)◶⟨<∘Fill⊸(⊣⌜)⋄{⊑⟜d⌜n|𝕩}⟩↕l
  }_fillBy_⊢⍟(l≠n)d
}
⥊ ↩ Deshape        ⊘ ⥊

Range←{
  I←{"↕𝕩: 𝕩 must consist of natural numbers"!Nat𝕩⋄↕𝕩}
  M←{"↕𝕩: 𝕩 must be a number or list"!1==𝕩⋄(0⌜𝕩)Fill(<⟨⟩)⥊⊸∾⌜´I⌜𝕩}
  IsArray◶I‿M 𝕩
}

ValidateRanks←{
  "⎉ or ⚇: 𝔽 result must have rank at most 1" ! 1≥=𝕩
  𝕩↩⥊𝕩
  "⎉ or ⚇: 𝔽 result must have 1 to 3 elements" ! (1⊸≤∧≤⟜3)≠𝕩
  "⎉ or ⚇: 𝔽 result must consist of integers" ! 1∧´Int⌜𝕩
  𝕩
}
_ranks ← {⟨2⟩⊘⟨1,0⟩ ((⊣-1+|)˜⟜≠⊑¨<∘⊢) ValidateRanks∘𝔽}
_depthOp_←{
  neg←0>n←𝕨𝔾_ranks𝕩 ⋄ F←𝔽
  _d←{
    R←(𝕗+neg)_d
    𝕨(×⟜2⊸+´2 Reshape (neg∧𝕗≥0)∨(0⌈𝕗)≥Pair○≡)◶⟨R¨⋄R⟜𝕩⌜∘⊣⋄(𝕨R⊢)⌜∘⊢⋄F⟩𝕩
  }
  𝕨 n _d 𝕩
}
_rankOp_←{
  k←𝕨(Pair○= (0≤⊢)◶⟨⌊⟜-,0⌈-⟩¨ 𝔾_ranks)𝕩
  Enc←{
    f←(↕𝕨)⊏≢𝕩
    c←1×´s←𝕨Cell𝕩⋄i←s⥊↕c
    (f⥊((⥊𝕩)⊏˜i+c×⊢)⌜↕1×´f)˙_fillBy_{(<𝕩)⌜i} 𝕩
  }
  Enc↩(>⟜0×1+≥⟜=)◶⟨<⊢,Enc,<⌜⊢⟩
  > ((0⊑k)Enc𝕨) 𝔽¨ ((1-˜≠)⊸⊑k)Enc𝕩
}
_insert←{
  "˝: 𝕩 must have rank at least 1" ! 1≤=𝕩
  F←𝔽
  Id ← {
    s ← 1 Drop ≢𝕩
    JoinSh ← {"˝: Identity does not exist"!0<≠𝕨 ⋄ 𝕨×0<↕≠𝕨}
    s ¬∘IsJoin∘⊢◶⟨JoinSh⥊𝕩˙, Reshape⟜Identity⟩ f
  }
  𝕨 (0<≠)⊘1◶Id‿{𝕨F´<˘𝕩} 𝕩
}
˝ ← _insert


JoinTo←∨○(1<=)◶(∾○⥊)‿{
  s←𝕨Pair○≢𝕩
  a←1⌈´k←≠⌜s
  "𝕨∾𝕩: Rank of 𝕨 and 𝕩 must differ by at most 1" ! 1∧´1≥a-k
  c←(k¬a)+⟜(↕a-1)⊸⊏¨s
  "𝕨∾𝕩: Cell shapes of 𝕨 and 𝕩 must match" ! ≡´c
  l←0+´(a=k)⊣◶1‿(0⊑⊢)¨s
  (⟨l⟩∾0⊑c)⥊𝕨∾○⥊𝕩
} _fillBy_ IF

Rep ← Indices⊸⊏
Replicate ← (0<=∘⊣)◶{
  𝕨↩(0⊑⥊)⍟IsArray𝕨
  "/: Amounts to replicate must be natural numbers" ! Nat 𝕨
  e←r←𝕨
  ({e+↩r⋄1+𝕩}⍟{e=𝕨}˜`↕r×≠𝕩) ⊏ 𝕩
}‿{
  "𝕨/𝕩: Lengths of components of 𝕨 must match 𝕩" ! 𝕨=○≠𝕩
  𝕨 Rep 𝕩
} _onAxes_ (1-0=≠) _fillBy_ ⊢

↑ ← Prefixes       ⊘ Take
↓ ← Suffixes       ⊘ Drop
↕ ↩ Range          ⊘ Windows
⌽ ← Reverse        ⊘ (Rot _onAxes_ 0)
/ ← Indices        ⊘ Replicate
» ← FC⊸ShiftBefore ⊘ ShiftBefore _fillBy_ (⊢⊘IF)
« ← FC⊸ShiftAfter  ⊘ ShiftAfter  _fillBy_ (⊢⊘IF)

_group←{
  "⊔: Grouping argument must consist of integers" ! 1∧´Int⌜𝕩
  "⊔: Grouping argument values cannot be less than ¯1" ! 1∧´¯1≤𝕩
  GL←GroupLen⋄𝕩↩𝕨(-˜⟜≠{GL↩(𝕨⊑𝕩)GL⊢⋄𝕨↑𝕩}⊢)⍟(0⊘⊣)𝕩
  d←(l←GL𝕩)GroupOrd𝕩
  i←0⋄(𝔽{𝕩⋄(i↩i+1)⊢i⊑d}⌜∘↕)⌜l
}
GroupInds←{
  "⊔𝕩: 𝕩 must be a list" ! 1==𝕩
  G←⊢_group
  (1<≡)◶⟨
    ↕∘0             Fill G
    ((⊢Fill⥊⟜⟨⟩)0⌜) Fill (<<⟨⟩) ∾⌜⌜´ {⊏⟜(⥊↕≢𝕩)⌜ G⥊𝕩}⌜
  ⟩ 𝕩
}
GroupGen←{
  "𝕨⊔𝕩: 𝕩 must be an array" ! IsArray 𝕩
  𝕨↩Pair∘ToArray⍟(2>≡)𝕨
  "𝕨⊔𝕩: Compound 𝕨 must be a list" ! 1==𝕨
  n←0+´r←=⌜𝕨
  "𝕨⊔𝕩: Total rank of 𝕨 must be at most rank of 𝕩" ! n≤=𝕩
  ld←(Join≢⌜𝕨)-n↑≢𝕩
  "𝕨⊔𝕩: Lengths of 𝕨 must equal to 𝕩, or one more only in a rank-1 component" ! 1∧´(0⊸≤∧≤⟜(r/1=r))ld
  dr←r⌊(0»+`r)⊏ld∾⟨0⟩
  l←≠⌜𝕨↩⥊⌜𝕨 ⋄ LS←∾⟜(n Cell 𝕩) Reshape 𝕩˙
  S←⊏⟜(LS⟨1×´l⟩)
  (LS 0⌜𝕨) Fill dr (1≠≠∘⊢)◶⟨S _group○(0⊸⊑), S⌜ ·+⌜⌜´ (⌽×`1»⌽l) × ⊢_group¨⟩ 𝕨
}

Pick1←{
  "𝕨⊑𝕩: Indices in compound 𝕨 must be lists" ! 1==𝕨
  "𝕨⊑𝕩: Index length in 𝕨 must match rank of 𝕩" ! 𝕨=○≠s←≢𝕩
  "𝕨⊑𝕩: Indices in 𝕨 must consist of integers" ! 1∧´Int⌜𝕨
  "𝕨⊑𝕩: Index out of range" ! 1∧´𝕨(≥⟜-∧<)s
  𝕨↩𝕨+s×𝕨<0
  (⥊𝕩)⊑˜0(⊑⟜𝕨+⊑⟜s×⊢)´-↕⊸¬≠𝕨
}
Pickd←(0∨´IsArray⌜∘⥊∘⊣)◶Pick1‿{Pickd⟜𝕩⌜𝕨}
Pick←IsArray◶⥊‿⊢⊸Pickd

# Sorting
CmpLen ← {
  e←𝕨-˜○(0∨´0⊸=)𝕩
  𝕨(e=0)◶⟨0,e⟩‿{
    c←×𝕨-○≠𝕩
    r←𝕨⌊○≠𝕩
    l←𝕨{
      i←0+´∧`𝕨=𝕩
      m←1×´⊑⟜𝕨⌜↕i
      {c↩×-´𝕩⋄m↩m×⌊´𝕩}∘(⊑¨⟜𝕨‿𝕩)⍟(r⊸>)i
      m
    }○(((-1+↕r)+≠)⊸{⊑⟜𝕩⌜𝕨})𝕩
    ⟨l,c⟩
  }𝕩
}
_getCellCmp ← {
  Ci←𝔽⋄l←𝕨⋄c←𝕩
  Cc←{
    a←𝕨⋄b←𝕩
    S←(l⊸=)◶{S∘(1+𝕩)⍟(0⊸=)a Ci○(𝕩⊸+)b}‿c
    S 0
  }
  (1≠l)⊑(𝕩⍟(0⊸=)𝔽)‿Cc
}

_binSearch ← {
  B ← 𝔽
  {
    R←{𝕨{a←B m←𝕩+h←⌊𝕨÷2⋄(h+a×2|𝕨)R a⊑𝕩‿m}⍟(>⟜1)𝕩}
    1+(𝕩+1)R ¯1
  }⍟(0⊸<)
}
_bins←{
  c←1-˜=𝕨
  "⍋ or ⍒: Rank of 𝕨 must be at least 1" ! 0≤c
  "⍋ or ⍒: Rank of 𝕩 must be at least cell rank of 𝕨" ! c≤=𝕩
  lw←1×´sw←1 Cell 𝕨
  cw←lw 𝔽○(⊑⟜(⥊𝕨)) _getCellCmp 0
  "⍋ or ⍒: 𝕨 must be sorted" ! 0⊸<◶⟨1,1∧´0≤˜·cw⟜(lw⊸+)⌜lw×↕∘-⟜1⟩≠𝕨
  cx←c-˜=𝕩
  sx←cx Cell ToArray 𝕩 ⋄ lc←sw CmpLen sx
  cc ← (⊑⟜(⥊𝕨))⊸𝔽⟜(⊑⟜(⥊𝕩)) _getCellCmp´ lc
  B←(1×´sw)⊸×⊸Cc≤0˜
  0 Fill (≠𝕨)⊸{B⟜𝕩 _binSearch 𝕨}⌜ (1×´sx) × ⥊⟜(↕1×´⊢)⊑⟜(≢𝕩)⌜↕cx
}

⚇ ← _depthOp_
⎉ ← _rankOp_
⍋ ← Cmp  _grade_ 0 ⊘ (Cmp  _bins)
⍒ ← Cmp˜ _grade_ 1 ⊘ (Cmp˜ _bins)

# Searching
_search←{ # 0 for ∊˜, 1 for ⊐
  ind ← 𝕗
  red ← 𝕗⊑⟨¬∧˝,+˝∧`⟩
  0 Fill {
    c←1-˜=𝕨
    "p⊐𝕩 or 𝕨∊p: p must have rank at least 1" ! 0≤c
    "p⊐n or n∊p: Rank of n must be at least cell rank of p" ! c≤=𝕩
    𝕨 ∧○(8<≠∘⥊)◶⟨
      (0<≠𝕨)◶⟨0⎉c∘⊢, Red≢⌜○((0<c)◶⟨⊢,<⎉c⟩)⟩
      { g←⌽⍒𝕨 ⋄ i←g⊏˜0⌈1-˜(g⊏𝕨)⍋𝕩 ⋄ (≠𝕨)(⊣+i⊸-⊸×)⍟ind(i⊏𝕨)≡⎉c𝕩 }
    ⟩ ToArray𝕩
  }
}
PermInv ← 1¨⊸GroupOrd
_self←{
  "∊𝕩 or ⊐𝕩: 𝕩 must have rank at least 1" ! 1≤=𝕩
  g←⍋𝕩
  0 Fill (PermInv g) ⊏ g 𝔽 0⊸<◶⟨1,-⟜1≢○(⊑⟜(g⊏<˘⍟(1<=)𝕩))⊢⟩⌜↕≠𝕩
}
SelfClas ← (PermInv∘⍋∘/˜⊏˜1-˜+`∘⊢) _self
Find←{
  r←=𝕨
  "⍷𝕩: Rank of 𝕨 cannot exceed rank of 𝕩" ! r≤=𝕩
  0 Fill 𝕨 ≡⎉r ((1+r-⊸↑≢𝕩)⌊≢𝕨)⊸↕⎉r 𝕩
}○ToArray

≍ ← >∘Pair _fillBy_ (⊢⊘IF)
∾ ↩ Join           ⊘ JoinTo
⊔ ← GroupInds      ⊘ GroupGen
⊐ ← SelfClas       ⊘ (1 _search)
∊ ← ⊢_self         ⊘ (0 _search˜)

ReorderChk←{
  "𝕨⍉𝕩: 𝕨 must have rank at most 1" ! 1≥=𝕨
  "𝕨⍉𝕩: Length of 𝕨 must not exceed rank of 𝕩" ! 𝕨≤○≠≢𝕩
  "𝕨⍉𝕩: 𝕨 must consist of natural numbers" ! 1∧´Nat⌜⥊𝕨
}
ReorderAxesSub←{
  (𝕨⊸⊏Pick𝕩˙)⌜↕⌊´⌜𝕨⊔≢𝕩
} _fillBy_ ⊢
ReorderAxes←{
  𝕨 ReorderChk 𝕩
  𝕨↩⥊𝕨
  r←(=𝕩)-0+´¬∊𝕨
  "𝕨⍉𝕩: Skipped result axis" ! 1∧´𝕨<r
  (𝕨∾𝕨(¬∘∊˜/⊢)↕r) ReorderAxesSub 𝕩
}
ReorderAxesInv←{
  𝕨 ReorderChk 𝕩
  𝕨↩⥊𝕨
  r←=𝕩
  IA 1∧´(∊∧<⟜r)𝕨
  (PermInv 𝕨∾𝕨(¬∘∊˜/⊢)↕r) ReorderAxesSub 𝕩
}
⍉ ← Transpose      ⊘ ReorderAxes

OccurrenceCount ← 0 Fill ⊐˜(⊢-⊏)⍋∘⍋
ProgressiveIndexOf ← 0 Fill {
  c←1-˜=𝕨
  "⊒: Rank of 𝕨 must be at least 1" ! 0≤c
  "⊒: Rank of 𝕩 must be at least cell rank of 𝕨" ! c≤=𝕩
  𝕨⊐○(((≢∾2˙)⥊≍˘⟜OccurrenceCount⍟(0<≠)∘⥊) 𝕨⊸⊐)𝕩
}

⊏ ↩ FirstCell      ⊘ (ToArray⊸(SelSub _onAxes_ 1)) _fillBy_ ⊢
⊑ ↩ First          ⊘ Pick
◶ ↩ {𝕨((𝕨𝔽𝕩)⊑𝕘){𝔽}𝕩}  # Same definition, new Pick
⁼ ← {Inverse 𝕗}

_repeat_←{
  n←𝕨𝔾𝕩
  l←u←0
  {"⍟: Repetition numbers in 𝕨 must be integers"!Int𝕩⋄l↩l⌊𝕩⋄u↩u⌈𝕩}⚇0 n
  b←𝕨{𝕏⊣}˙⊘{𝕨˙{𝔽𝕏⊣}}0
  i←⟨𝕩⟩⋄P←B⊸{𝕎`i∾↕𝕩}
  pos←𝕗 P u
  neg←𝕗 0⊸<◶⟨i,Inverse⊸P⟩ -l
  (|⊑<⟜0⊑pos‿neg˙)⚇0 n
}

⍟ ↩ _repeat_
⥊ ↩ Deshape        ⊘ Reshape
⌾ ← _under_
⊒ ← OccurrenceCount⊘ ProgressiveIndexOf
⍷ ← ∊⊸/            ⊘ Find

_lookup_ ← {
  s ← 2×↕(≠𝕘)÷2
  (s⊏𝕘) _glyphLookup_ (((1+s)⊏𝕘)∾<𝕗)
}
Identity ← {𝕏0} ("´: Identity not found"!0˙) _lookup_ ⟨
  '+',0 , '-',0
  '×',1 , '÷',1
  '⋆',1 , '¬',1
  '⌊',∞ , '⌈',¯∞
  '∨',0 , '∧',1
  '≠',0 , '=',1
  '>',0 , '≥',1
⟩

IA ← "⁼: Inverse failed"⊸!
IX ← "⁼: Inverse does not exist"⊸!
INF← "⁼: Inverse not found"!0˙
_invChk_ ← {i←𝕨𝔽𝕩⋄IX 𝕩≡𝕨𝔾i⋄i}
GroupIndsInv ← {
  IA 2=≡𝕩
  IX 1∧´1==⌜𝕩
  j←∾𝕩
  IX 1∧´Nat⌜j
  IX 1∧´j>∾¯1»¨𝕩
  g←GroupLen j
  IX 1∧´g≤1
  o←/¬g
  (⍋j∾o)⊏(/≠¨𝕩)∾¯1¨o
}
GroupInv ← {
  IA 1==𝕨
  IA 1∧´Nat⌜𝕨
  i←⊔𝕨
  IX i≡○(≠¨)𝕩
  i ⍋⊸⊏○∾ 𝕩
}
PrimInverse ← INF _lookup_ ⟨
  '+', +⊘(-˜)
  '-', -
  '×', ⊢⊘(÷˜)
  '÷', ÷
  '⋆', Log _perv
  '√', ט⊘(⋆˜)
  '∧', ⊢_invChk_∧⊘(÷˜)
  '∨', ⊢_invChk_∨⊘(-˜÷1-⊣)
  '¬', ¬
  '<', {IX IsArray𝕩⋄IX 0==𝕩⋄⊑𝕩}⊘(IA∘0)
  '⊢', ⊢
  '⊣', ⊢⊘(⊢⊣IX∘≡)
  '∾', IA∘0 ⊘ {d←𝕩-○=𝕨⋄IX(0⊸≤∧≤⟜1)d⋄l←d◶1‿≠𝕨⋄IX l≤≠𝕩⋄IX 𝕨≡d◶⟨⊏,l⊸↑⟩𝕩⋄l↓𝕩}
  '≍', {IX 1=≠𝕩⋄⊏𝕩} ⊘ {IX 2=≠𝕩⋄IX 𝕨≡⊏𝕩⋄1⊏𝕩}
  '↑', ¯1⊸⊑_invChk_↑ ⊘ (IA∘0)
  '↓',    ⊑_invChk_↓ ⊘ (IA∘0)
  '↕', ≢_invChk_↕ ⊘ (IA∘0)  # Should trace edge and invChk
  '⌽', ⌽ ⊘ (-⊸⌽)
  '⍉', TransposeInv ⊘ ReorderAxesInv
  '/', {IA 1==𝕩⋄IA 1∧´Nat⌜𝕩⋄IX(1∧´¯1⊸↓≤1⊸↓)𝕩⋄GroupLen𝕩}⊘(IA∘0)
  '⊔', GroupIndsInv ⊘ GroupInv
⟩
⌜ ↩ {𝕨𝔽⌜_fillByPure_𝔽○ToArray𝕩}
_inv_ ← {𝕘⋄𝕨𝔽𝕩}
AtopInverse ← {(𝕏𝕎)⊘(𝕏⟜𝕎)}○{Inverse𝕩}
SwapInverse ← INF _lookup_ ⟨
  '+', ÷⟜2⊘(-˜)
  '-', IA∘0⊘+
  '×', √⊘(÷˜)
  '÷', IA∘0⊘×
  '⋆', IA∘0⊘√
  '√', IA∘0⊘(÷Log)
  '∧', √⊘(÷˜)
  '∨', (¬√∘¬)⊘(-˜÷1-⊣)
  '¬', IA∘0⊘(+-1˙)
⟩
Mod1Inverse ← INF˙ _lookup_ ⟨
  '˜', SwapInverse
  '¨', {𝕏⁼¨                     ⊣·IX 0<≡∘⊢}
  '⌜', {𝕏⁼⌜⊘(IA∘0)              ⊣·IX 0<≡∘⊢}
  '˘', {(IX∘IsArray⊸⊢𝕏⁼)˘       ⊣·IX 0<=∘⊢}
  '`', {(⊏∾¯1⊸↓𝕏1⊸↓)⍟(1<≠)⊘(»𝕏⊢)⊣·IX 0<=∘⊢}∘{𝕏⁼¨}
⟩ {
  0⊸⊑ {𝕏𝕨}⟜𝔽 1⊸⊑
}
IsConstant ← (3≤Type)◶⟨1 ⋄ ∧´ ⟨4⊸≡,'˙'_isGlyph⟩ {𝕎𝕩}¨ 0‿¯1⊏{Decompose𝕩}⟩
Mod2Inverse ← INF˙ _lookup_ ⟨
  '∘', AtopInverse
  '○', {Fi←𝕎⁼⋄𝕏⁼ Fi⊘(𝕏⊸Fi)}
  '⌾', {𝕎⁼⌾𝕏}  # Need to verify for computation Under
  '⍟', Int∘⊢◶⟨IA∘0˙,0⊸≤◶{𝕎⍟(-𝕩)_invChk_(𝕎⍟𝕩)}‿{𝕎⍟(-𝕩)}⟩
  '⊘', {(𝕎⁼)⊘(𝕏⁼)}
  '⊸', IsConstant∘⊣ ⊣◶{INF⊘𝕏}‿⊢ {𝕎⊸(𝕏⁼)}
  '⟜', {(𝕨IsConstant∘⊢◶⟨IA∘0˙,{𝕩𝕎{SwapInverse𝕗}⊢}⟩𝕩)⊘(𝕏⁼𝕎⁼)}
⟩ { inv˙⊸=◶⟨𝔽,{𝕏_inv_𝕎}˙⟩ } {
  0‿2⊸⊏ {𝕏´𝕨}⟜𝔽 1⊸⊑
}
TrainInverse ← {
  f‿g‿h←𝕩
  K←¬IsConstant
  f K∘⊣◶⟨{𝕏⁼{𝕨𝔽𝔾𝕩}(𝕨G⁼⊢)},K∘⊢◶⟨{𝕎⁼𝕩G{SwapInverse𝕗}⊢},INF˙⟩⟩ h
}
FuncInverse ← (⊑ ⊣◶⟨
  PrimInverse∘⊑⊢                         # 0 primitive
  ("Cannot currently invert blocks"!0˙)˙ # 1 block
  AtopInverse´⊢                          # 2-train
  TrainInverse                           # 3-train
  Mod1Inverse                            # 4 1-modifier
  Mod2Inverse                            # 5 2-modifier
⟩ 1⊸↓) {Decompose𝕩}
Inverse ← Type◶(3‿1‿2/{⊢⊣𝕩IX∘≡⊢}‿FuncInverse‿("Cannot invert modifier"!0˙))
⁼ ↩ {𝕗 (≢∧INF˙⊸≢)◶0‿(5‿_inv_≢0‿¯2⊏Decompose∘⊢)◶⊢‿{𝕏_inv_(𝕎_invChk_𝕏)} Inverse 𝕗}

structPrimClass ← {(∾𝕩)_glyphLookup_((/∾≠)≠¨𝕩)} ⥊¨ ⟨
  '⊢'‿'⊣'‿'˜'‿'∘'‿'○'‿'⊸'‿'⟜'‿'⊘'‿'◶'
  '='‿'≠'‿'≢'
  '<'
  '≍'
  '↕'‿'/'‿'»'‿'«'‿'⊔'
  '⥊'‿'↑'‿'↓'‿'⌽'‿'⍉'‿'⊏'‿'⊑'
# >
# ∾
# ˘⎉¨⌜
# ⚇
⟩