avoid prototype issues

IotaUnderbar.aplf

@@ -1,5 +1,5 @@
-IotaUnderbar←{ ⍝ ⍸ ⍝ just ⎕IO
-     ⎕IO←0
+IotaUnderbar←{ ⍝ ⍸ ⎕IO←0 for monadic but ⎕IO←1 for dyadic
+     ⎕IO←×⎕NC'⍺'
      ⍺←⊢
      ⍺⍸⍵
  }

LeftShoe.aplf

@@ -1,4 +1,4 @@
-LeftShoe←{ ⍝ ⊂ ⍝ just ⎕IO
+LeftShoe←{ ⍝ ⊂ just ⎕IO
      0=⎕NC'⍺':⊂⍵
      ⍺⊂[⎕IO]⍵
  }

README.md

@@ -40,18 +40,19 @@ Now you have three options:
 |[DownTack](DownTack.aplf)|`⊤`|transposed and extend scalar|
 |[Epsilon](Epsilon.aplf)|`∊`|on major cells|
 |[Iota](Iota.aplf)|`⍳`|noticing 1-element vector|
-|[IotaUnderbar](IotaUnderbar.aplf)|`⍸`|⍝ just `⎕IO`|
-|[LeftShoe](LeftShoe.aplf)|`⊂`|⍝ just `⎕IO`|
+|[IotaUnderbar](IotaUnderbar.aplf)|`⍸`|`⎕IO←0` for monadic but `⎕IO←1` for dyadic|
+|[LeftShoe](LeftShoe.aplf)|`⊂`|just `⎕IO|`
 |[LeftShoeUnderbar](LeftShoeUnderbar.aplf)|`⊆`|on major cells|
 |[Plus](Plus.aplf)|`+`|purely numeric|
 |[QuadDivide](QuadDivide.aplf)|`⌹`|high rank|
 |[Query](Query.aplf)|`?`|high rank|
-|[RightShoe](RightShoe.aplf)|`⊃`|⍝ just `⎕IO`|
+|[RightShoe](RightShoe.aplf)|`⊃`|just `⎕IO|`
 |[SlashBar](SlashBar.aplf)|`⌿`|only replicate first|
 |[Squad](Squad.aplf)|`⌷`|but sane|
 |[Tilde](Tilde.aplf)|`~`|on major cells|
 |[UpShoe](UpShoe.aplf)|`∩`|on major cells|
 |[UpTack](UpTack.aplf)|`⊥`|transposed|
 |[_BackSlash](_BackSlash.aplo)|`\`|scan first and outer product|
-|[_Diaeresis](_Diaeresis.aplo)|`¨`|ignoring empty arrays|
+|[_CircleDiaeresis_](_CircleDiaeresis_.aplo)|`⍤`|but handling empties|
+|[_Diaeresis](_Diaeresis.aplo)|`¨`|handling empty arrays with failing prototype|
 |[_Slash](_Slash.aplo)|`/`|only reduce first|

RightShoe.aplf

@@ -1,4 +1,4 @@
-RightShoe←{ ⍝ ⊃ ⍝ just ⎕IO
+RightShoe←{ ⍝ ⊃ just ⎕IO
      ⍺←⊢
      ⎕IO←0
      ⍺⊃⍵

_BackSlash.aplo

@@ -1,4 +1,5 @@
-_BackSlash←{ ⍝ \ scan first and outer product
-     0=⎕NC'⍺':⍺⍺⍀⍵
+ _BackSlash←{ ⍝ \ scan first and outer product
+     0=⎕NC'⍺':⍺⍺⌿_Diaeresis↑∘⍵¨(~⎕IO)+⍳≢⍵
+     0∩shape←∊⍴¨⍺ ⍵::shape⍴⎕NS ⍬
      ⍺∘.⍺⍺ ⍵
  }

_Diaeresis.aplo

@@ -1,5 +1,6 @@
-_Diaeresis←{ ⍝ ¨ ignoring empty arrays
+ _Diaeresis←{ ⍝ ¨ handling empty arrays with failing prototype
      ⍺←⊢
-     (0∘∊∘∊∧0∊≢¨)⍴¨⍺ ⍵ ⍵:⍵
+     r←⍺⊢¨⍵
+     0⍴⍨0∊⍴r::(⍴r)⍴⎕NS ⍬
      ⍺ ⍺⍺¨⍵
  }

_JotDiaeresis_.aplo

@@ -0,0 +1,7 @@
+ _JotDiaeresis_←{ ⍝ ⍤ but handling empties
+     rank←⌽3⍴⌽⍵⍵
+     0=⎕NC'⍺':↑⍺⍺ _Diaeresis⊂⍤(⊃rank)⊢⍵
+     a←⊂⍤(⊃1⌽rank)⊢⍺
+     w←⊂⍤(⊃2⌽rank)⊢⍵
+     ↑⍺ ⍺⍺ _Diaeresis ⍵
+ }

prime.apln

@@ -2,6 +2,15 @@
     ⎕IO←1 ⋄ ⎕ML←1
     Err←{⍞←⍵,⎕UCS 13}
 
+    ∇ {text}←UpdateReadme path;head;tail;file
+      file←path,'/README.md'
+      text←⊃⎕NGET file 1
+      head←(3↑¨text)⍳⊂'| -'
+      tail←'⎕\S+'⎕R'`&`'{'|[',⍵,'](',⍵,'.apl',('  fo'⊃⍨⊃##.⎕NC ⍵),')',⊃'⍝ (.) (.*)'⎕S'|`\1`|\2|'⊃##.⎕NR ⍵}¨##.⎕NL-3 4
+      text←tail,⍨head↑text
+      file 1 ⎕NPUT⍨⊂text
+    ∇
+
     ∇ {ns}←Repl target;input;n;v
       2022⌶⍣('W'=⊃⊃# ⎕WG'APLVersion')⊤⍨⍬
       :If ×≢target