Modulo shift/rotate counts

doc/DRAWL.md

@@ -158,6 +158,8 @@ LISP 1.5 Manual: https://archive.org/details/bitsavers_mitrlelisprammersManual2e
 
 LISP 1.5 Primer: https://www.softwarepreservation.org/projects/LISP/book/Weismann_LISP1.5_Primer_1967.pdf
 
+P-LISP Manual (newer than LISP 1.5): https://archive.org/details/gLISP/gnosisLISPManual
+
 Apple Numerics Manual (SANE): https://vintageapple.org/inside_o/pdf/Apple_Numerics_Manual_Second_Edition_1988.pdf
 
 Video showing DRAWL in action: https://youtu.be/wBMivg6xfSg

src/lisp/s-math.pla

@@ -710,6 +710,10 @@ def natv_shift(symptr, expr)
     //
     // Shift right
     //
+    if shift < -31
+      bitval[1] = bitval[1] < 0 ?? $FFFF :: 0
+      bitval[0] = bitval[1]
+    else
       while shift < 0
         bitval[0] = bitval[0] >> 1
         if bitval[1] & 1
@@ -720,10 +724,15 @@ def natv_shift(symptr, expr)
         bitval[1] = bitval[1] >> 1
         shift++
       loop
+    fin
   else
     //
     // Shift left
     //
+    if shift > 31
+      bitval[0] = 0
+      bitval[1] = 0
+    else
       while shift > 0
         bitval[1] = bitval[1] << 1
         if bitval[0] & $8000
@@ -733,6 +742,7 @@ def natv_shift(symptr, expr)
         shift--
       loop
     fin
+  fin
   return new_int(bitval[0], bitval[1])
 end
 
@@ -746,6 +756,7 @@ def natv_rotate(symptr, expr)
   symptr    = eval_int(expr=>cdr)
   rotate    = symptr=>intval[0]
   if rotate < 0
+    rotate = rotate | $FFFFFFE0
     while rotate < 0
       wrap      = bitval[0] & 1 ?? $8000 :: 0
       bitval[0] = bitval[0] >> 1
@@ -758,6 +769,7 @@ def natv_rotate(symptr, expr)
       rotate++
     loop
   else
+    rotate = rotate & $0000001F
     while rotate > 0
       wrap      = bitval[1] & $8000 ?? 1 :: 0
       bitval[1] = bitval[1] << 1