Data update

Task/Truncatable-primes/REXX/truncatable-primes.rexx

@@ -1,38 +1,76 @@
-/*REXX program finds largest  left─ and right─truncatable  primes ≤ 1m  (or argument 1).*/
-parse arg hi .;      if hi==''  then hi= 1000000 /*Not specified? Then use default of 1m*/
-call genP                                        /*generate some primes,  about  hi ÷ 2 */
-                                                 /* [↓]  find largest left truncatable P*/
-  do L=#  by -1  for #                           /*search from top end;  get the length.*/
-       do k=1  for length(@.L); _= right(@.L, k) /*validate all left truncatable primes.*/
-       if \!._  then iterate L                   /*Truncated number not prime?  Skip it.*/
-       end   /*k*/
-  leave                                          /*egress, found left truncatable prime.*/
-  end        /*L*/
-                                                 /* [↓]  find largest right truncated P.*/
-  do R=#  by -1  for #                           /*search from top end;  get the length.*/
-       do k=1  for length(@.R);  _= left(@.R, k) /*validate all right truncatable primes*/
-       if \!._  then iterate R                   /*Truncated number not prime?  Skip it.*/
-       end   /*k*/
-  leave                                          /*egress, found right truncatable prime*/
-  end        /*R*/
+/*REXX program finds largest left- and right-truncatable primes less than hi   */
+Parse Arg hi .
+If hi=='' Then
+  hi=1000000                            /* Not specified? Then use default     */
+Call genP                               /* generate primes up to hi            */
 
-say 'The largest  left─truncatable prime ≤'        hi        " is "       right(@.L, w)
-say 'The largest right─truncatable prime ≤'        hi        " is "       right(@.R, w)
-exit                                             /*stick a fork in it,  we're all done. */
-/*──────────────────────────────────────────────────────────────────────────────────────*/
-genP: !.= 0;                     w= length(hi)   /*placeholders for primes;  max width. */
-      @.1=2;  @.2=3;  @.3=5;  @.4=7;  @.5=11     /*define some low primes.              */
-      !.2=1;  !.3=1;  !.5=1;  !.7=1;  !.11=1     /*   "     "   "    "     flags.       */
-                        #=5;     s.#= @.# **2    /*number of primes so far;     prime². */
-                                                 /* [↓]  generate more  primes  ≤  high.*/
-        do j=@.#+2  by 2  for max(0, hi%2-@.#%2-1)      /*find odd primes from here on. */
-        parse var j '' -1 _; if     _==5  then iterate  /*J divisible by 5?  (right dig)*/
-                             if j// 3==0  then iterate  /*"     "      " 3?             */
-                             if j// 7==0  then iterate  /*"     "      " 7?             */
-                                                 /* [↑]  the above five lines saves time*/
-               do k=5  while s.k<=j              /* [↓]  divide by the known odd primes.*/
-               if j // @.k == 0  then iterate j  /*Is  J ÷ X?  Then not prime.     ___  */
-               end   /*k*/                       /* [↑]  only process numbers  ≤  √ J   */
-        #= #+1;    @.#= j;    s.#= j*j;   !.j= 1 /*bump # of Ps; assign next P;  P²; P# */
-        end          /*j*/
-     return
+/* find largest left truncatable Prime */
+Do l=prime.0 By -1                      /* search from top end;                */
+  left.0=length(prime.l)
+  Do k=1 For length(prime.l)
+    _=right(prime.l,k)                  /* validate left truncatable ptime     */
+    left.k=_
+    If \is_prime._ Then
+      Iterate l                         /* Truncated number not prime?  Skip   */
+    End
+  Leave
+  End
+
+/* find largest right truncated Prime */
+Do r=prime.0 By -1                      /* search from top end;                */
+  right.0=length(prime.r)
+  Do k=1 For length(prime.r)
+    _=left(prime.r,k)
+    right.k=_
+    If \is_prime._ Then
+      Iterate r                         /* Truncated number not prime?  Skip   */
+    End
+  Leave
+  End
+
+Say 'The largest  left-truncatable prime smaller than' hi 'is' prime.l
+do i=left.0-1 to 1 By -1
+  say right(left.i,66)
+  End
+Say 'The largest right-truncatable prime smaller than' hi 'is' prime.r
+do i=right.0-1 to 1 By -1
+  say copies(' ',60)right.i
+  End
+Exit                                    /* stick a fork in it,  we're all done */
+/*-----------------------------------------------------------------------------*/
+genp:
+  Call time 'R'
+  Call init 2 3 5 7 11 13 17 19
+  Do j=21 to hi By 2
+    Select
+      When right(j,1)=5 Then Iterate
+      When j//3==0 Then Iterate
+      When j//7==0 Then Iterate
+      Otherwise Nop
+      End
+    Do k=5 While s.k<=j
+      If j//prime.k==0 Then
+        Iterate j
+      End
+    Call store j                        /* j is prime                          */
+    End
+  Say prime.0 'primes smaller than' hi '--'  time('E') 'seconds'
+  Return
+
+init:
+  Parse Arg plist
+  is_prime.=0
+  prime.=0
+  Do i=1 To words(plist)
+    Call store word(plist,i)
+    End
+  Return
+
+store:
+  Parse Arg p
+  z=prime.0+1
+  prime.z=p
+  s.z=p*p
+  prime.0=z
+  is_prime.p=1
+  Return

Task/Truncatable-primes/Uiua/truncatable-primes.uiua

@@ -0,0 +1,10 @@
+Mag ← 6
+MaxP ← ⁿ:10⌊÷2Mag
+# Pre-calculate primes up to root of largest n
+Primes ← ⇌◌⍢(▽≠0◿⊢..⟜(⊂⊢)|>0⧻.):[]⊂2↘1+1×2⇡⌊÷2 MaxP # Build primes
+IsPrime ← ⨬(/↧≡(≠0◿)|1)∊:,,Primes
+RAdd ← ♭⊞(+×10):1_3_7_9                   # Add suffixes
+LAdd ← ♭⊞+×ⁿ:10⌈ₙ10⊢,+1⇡9                 # Add prefixes
+LastTP! ← ⊡¯1⍥(▽⊸≡IsPrime^!)-1Mag 2_3_5_7 # Build and filter
+$"Right truncating: _"LastTP!RAdd
+$"Left truncating: _"LastTP!LAdd