TLS Chapter #08 Examples in Oz
% Defined in previous chapters
fun {Add1 N} N + 1 end
fun {IsAtomS X}
   if {IsAtom X} andthen {Not X == nil}
      then true
      else {IsNumber X}
   end
end

%%%%%%%%%%%%%%%%%%% The Little Schemer - Chapter - 8 %%%%%%%%%%%%%%%%%%%%%%

% 8.9 - 8.10
fun {RemberF Test L A}
   case L
   of nil then nil
   [] H|T then
      if {Test A H}
         then T
         else H|{RemberF Test T A}
      end
   end
end

% 8.3
{Browse 3#{RemberF fun {$ X Y} X==Y end [b c a] a}}

% 8.4
{Browse 4#{RemberF fun {$ X Y} X==Y end [b c a] c}}

% 8.6
local Test A L in
   Test = fun {$ X Y} X==Y end
   A = 5
   L = [6 2 5 3]
   {Browse 6#{RemberF Test L A}}
end

% 8.7
local Test A L in
   Test = fun {$ X Y} X==Y end
   A = jelly
   L = [jelly beans are good]
   {Browse 7#{RemberF Test L A}}
end

% 8.8
local Test A L in
   Test = fun {$ X Y} X==Y end
   A = [pop corn]
   L = [lemonade [pop corn] and [cake]]
   {Browse 8#{RemberF Test L A}}
end

% 8.21
fun {EqC A}
   fun {$ X}
      X == A
   end
end

% 8.22
local K in
   K = salad
   {Browse 22#{EqC K}}
end

% 8.23
EqSalad = {EqC salad}

% 8.24
local Y in
   Y = salad
   {Browse 24#{EqSalad Y}}
end

% 8.25
local Y in
   Y = tuna
   {Browse 25#{EqSalad Y}}
end

% 8.27
fun {RemberFC Test}
   fun {$ L A}
      case L
      of nil then nil
      [] H|T then
         if {Test A H}
            then T
            else H|{{RemberFC Test} T A}
         end
      end
   end
end

% 8.28
local Test in
   Test = fun {$ X Y} X==Y end
   {Browse 28#{RemberFC Test}}
end

% 8.29
RemberEq = {RemberFC fun {$ X Y} X==Y end}

% 8.30
local L A in
   A = tuna
   L = [tuna salad is good]
   {Browse 30#{RemberEq L A}}
end

% 8.33
local L A in
   A = tuna
   L = [shrimp salad and tuna salad]
   {Browse 33#{RemberEq L A}}
end

% 8.34
local A L in
   A = 'eq?'
   L = ['equal?' 'eq?' 'eqan?' 'eqlist?' 'eqpair?']
   {Browse 34#{{RemberFC fun {$ X Y} X==Y end} L A}}
end

% 8.35
fun {InsertLF Test}
   fun {$ L New Old}
      case L
      of nil then nil
      [] H|T then
         if {Test Old H}
            then New|H|T
            else H|{{InsertLF Test} T New Old}
         end
      end
   end
end

% 8.36
fun {InsertRF Test}
   fun {$ L New Old}
      case L
      of nil then nil
      [] H|T then
         if H == Old
            then H|New|T
            else H|{{InsertRF Test} T New Old}
         end
      end
   end
end

% 8.42
fun {SeqL L New Old}
   New|Old|L
end

% 8.43
fun {SeqR L New Old}
   Old|New|L
end

% 8.45
fun {InsertG Seq}
   fun {$ L New Old}
      case L of nil then nil
      [] H|T then
         if H == Old
            then {Seq T New Old}
            else H|{{InsertG Seq} T New Old}
         end
      end
   end
end

% 8.46
InsertL = {InsertG SeqL}

% 8.47
InsertR = {InsertG SeqR}

% 8.50
InsertL1 = {InsertG fun {$ L New Old} New|Old|L end}

% 8.52
fun {Subst_ L New Old}
   case L
   of nil then nil
   [] H|T then
      if H == Old
         then New|T
         else H|{Subst_ T New Old}
      end
   end
end

% 8.54
fun {SeqS L New Old}
   New|L
end

% 8.55
Subst = {InsertG SeqS}

% 8.56
fun {SeqRem L New Old}
   L
end
fun {Rember L A}
   {{InsertG SeqRem} L false A}
end

local A L in
   A = sausage
   L = [pizza with sausage and bacon]
   {Browse 56#{Rember L A}}
end

% 8.59
fun {FirstSubExp AExp}
   case AExp
   of _|X|_ then X
   end
end
fun {SecondSubExp AExp}
   case AExp
   of _|_|Y|_ then Y
   end
end
fun {Operator AExp}
   case AExp
   of H|_ then H
   end
end
fun {Value_ NExp}
   if {IsNumber NExp}
      then NExp
      else
         case {Operator NExp}
         of '+' then {Value_ {FirstSubExp NExp}} + {Value_ {SecondSubExp NExp}}
         [] '*' then {Value_ {FirstSubExp NExp}} * {Value_ {SecondSubExp NExp}}
         [] '^' then {Pow {Value_ {FirstSubExp NExp}} {Value_ {SecondSubExp NExp}}}
         end
   end
end

% 8.61
fun {AtomToFunction AExp}
   case AExp
   of '+' then Number.'+'
   [] '*' then Number.'*'
   [] '^' then Pow
   end
end

% 8.62
local NExp in
   NExp = ['+' 5 3]
   {Browse 62#{AtomToFunction {Operator NExp}}}
end

% 8.63
fun {Value NExp}
   if {IsNumber NExp}
      then NExp
      else {{AtomToFunction {Operator NExp}}
               {Value {FirstSubExp NExp}}
               {Value {SecondSubExp NExp}}}
   end
end

% 8.66
fun {MultiRember L A}
   case L
   of nil then nil
   [] H|T then
      if A == H
         then {MultiRember T A}
         else H|{MultiRember T A}
      end
   end
end
fun {MultiRemberF Test}
   fun {$ L A}
      case L
      of nil then nil
      [] H|T then
         if {Test A H}
            then {{MultiRemberF Test} T A}
            else H|{{MultiRemberF Test} T A}
         end
      end
   end
end

% 8.67
local Test A Lat in
   Test = fun {$ X Y} X==Y end
   A = tuna
   Lat = [shrimp salad tuna salad and tuna]
   {Browse 67#{{MultiRemberF Test} Lat A}}
end

% 8.69
MultiRemberEq = {MultiRemberF fun {$ X Y} X==Y end}

% 8.74
EqTuna = {EqC tuna}

% 8.76
fun {MultiRemberT Test L}
   case L
   of nil then nil
   [] H|T then
      if {Test H}
         then {MultiRemberT Test T}
         else H | {MultiRemberT Test T}
      end
   end
end

% 8.77
local Test Lat in
   Test = EqTuna
   Lat = [shrimp salad tuna salad and tuna]
   {Browse 77#{MultiRemberT Test Lat}}
end

% 8.79
fun {MultiRemberAndCo Col L A}
   case L
   of nil then {Col nil nil}
   [] H|T then
      if H == A
         then {MultiRemberAndCo fun {$ NewLat Seen} {Col NewLat H|Seen} end T A}
         else {MultiRemberAndCo fun {$ NewLat Seen} {Col H|NewLat Seen} end T A}
      end
   end
end

% 8.80
fun {AFriend X Y}
   Y == nil
end

% 8.81
local A Lat Col in
   A = tuna
   Lat = [strawberries tuna and swordfish]
   Col = AFriend
   {Browse 81#{MultiRemberAndCo Col Lat A}}
end

% 8.82
local A Lat Col in
   A = tuna
   Lat = nil
   Col = AFriend
   {Browse 82#{MultiRemberAndCo Col Lat A}}
end

% 8.83
local A Lat Col in
   A = tuna
   Lat = [tuna]
   Col = AFriend
   {Browse 82#{MultiRemberAndCo Col Lat A}}
end

% 8.87
local Lat Col in
   Lat = [tuna]
   Col = AFriend
   fun {NewFriend0 NewLat Seen}
      {Col NewLat Lat.1 | Seen}
   end
end

% 8.88
fun {NewFriend NewLat Seen}
   {AFriend NewLat tuna | Seen}
end

% 8.93
fun {LatestFriend NewLat Seen}
   {AFriend and|NewLat Seen}
end

% 8.96
fun {LastFriend X Y}
   {Length X}
end
local Ls Col in
   Ls = [strawberries tuna and swordfish]
   Col = LastFriend
   {Browse 96#{MultiRemberAndCo Col Ls tuna}}
end

% 8.99
fun {MultiInsertL L New Old}
   case L
   of nil then nil
   [] H|T then
      if Old == H
         then New|H|{MultiInsertL T New Old}
         else H|{MultiInsertL T New Old}
      end
   end
end
fun {MultiInsertR L New Old}
   case L
   of nil then nil
   [] H|T then
      if Old == H
         then H|New|{MultiInsertR T New Old}
         else H|{MultiInsertR T New Old}
      end
   end
end

% 8.100
fun {MultiInsertLR L New OldL OldR}
   case L
   of nil then nil
   [] H|T then
      if H == OldL then
         New|OldL|{MultiInsertLR T New OldL OldR}
      elseif H == OldR then
         OldR|New|{MultiInsertLR T New OldL OldR}
      else
         H|{MultiInsertLR T New OldL OldR}
      end
   end
end

% 8.103
fun {MultiInsertLRAndCo Col L New OldL OldR}
   case L
   of nil then {Col nil 0 0}
   [] H|T then
      if H == OldL then
         {MultiInsertLRAndCo fun {$ NewLat L R} {Col New|OldL|NewLat {Add1 L} R} end T New OldL OldR}
      elseif H == OldR then
         {MultiInsertLRAndCo fun {$ NewLat L R} {Col OldR|New|NewLat L {Add1 R}} end T New OldL OldR}
      else
         {MultiInsertLRAndCo fun {$ NewLat L R} {Col H|NewLat L R} end T New OldL OldR}
      end
   end
end

% Note: Book doesn't give example Collector function
% %% 8.104
% local Col in
%    Col = ...
%    {Browse 104#{MultiInsertLRAndCo Col nil cranberries fish chips}
% end
%
% %% 8.111
% local Col New OldL OldR Lat in
%    Col = ...
%    New = salty
%    OldL = fish
%    OldR = chips
%    Lat = [chips and fish or fish and chips}
%    {Browse 111#{MultiInsertLRAndCo Col Lat New OldL OldR}
% end

% 8.114
fun {IsEven_ N}
   (N div 2) * 2 == N
end
fun {EvensOnly L}
   case L
   of nil then nil
   [] H|T then
      if {IsAtomS H}
         then
            if {IsEven_ H}
               then H|{EvensOnly T}
               else {EvensOnly T}
            end
         else {EvensOnly H}|{EvensOnly T}
      end
   end
end

% 8.115
local L in
   L = [[9 1 2 8] 3 10 [[9 9] 7 6] 2]
   {Browse 115#{EvensOnly L}}
end

% Note: Book doesn't give code for last else case
%% 8.119
fun {EvensOnlyAndCo Col L}
   case L
   of nil then {Col nil 1 0}
   [] H|T then
      if {IsAtomS H}
         then
            if {IsEven_ H}
               then {EvensOnlyAndCo fun {$ NewL P S} {Col H|NewL H*P S} end T}
               else {EvensOnlyAndCo fun {$ NewL P S} {Col NewL P H+S} end T}
            end
         else {EvensOnlyAndCo Col H}|{EvensOnlyAndCo Col T}
      end
   end
end

% %% 8.116
% local L in
%    L = [[9 1 28] 3 10 [[9 9] 7 6] 2]
%    {Browse 116#{EvensOnlyAndCo ... L}}
% end

% Note: This does not give correct result (see note on 8.119)
%% 8.126
fun {TheLastFriend NewL Product Sum}
   Sum|Product|NewL
end
local L in
   L = [[9 1 2 8] 3 10 [[9 9] 7 6] 2]
   {Browse 126#{EvensOnlyAndCo TheLastFriend L}}
end