new files

Task/Binary-search/Forth/binary-search.fth

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+defer (compare)
+' - is (compare) \ default to numbers
+
+: cstr-compare ( cstr1 cstr2 -- <=> ) \ counted strings
+  swap count rot count compare ;
+
+: mid ( u l -- mid ) tuck - 2/ -cell and + ;
+
+: bsearch ( item upper lower -- where found? )
+  rot >r
+  begin  2dup >
+  while  2dup mid
+         dup @ r@ (compare)
+         dup
+  while  0<
+         if   nip cell+   ( upper mid+1 )
+         else rot drop swap ( mid lower )
+         then
+  repeat drop nip nip             true
+  else   max ( insertion-point ) false
+  then
+  r> drop ;
+
+create test 2 , 4 , 6 , 9 , 11 ,   99 ,
+: probe ( n -- ) test 5 cells bounds bsearch . @ . cr ;
+1 probe \ 0 2
+2 probe \ -1 2
+3 probe \ 0 4
+10 probe \ 0 11
+11 probe \ -1 11
+12 probe \ 0 99