(*

LIB of B

new: --> LIB
add: LIB x B --> LIB
rem: LIB x B --> LIB
cko: LIB x B x P --> LIB
cki: LIB x B x P --> LIB
wait: LIB x B x P --> LIB
nah: LIB x B x P --> LIB
has: LIB x B --> boolean
num: LIB x B --> int
avail: LIB x B --> int

variables
book: i,j,k
person: m,n,p
lib: S,T

*)

datatype lib =
  new
  | add of lib * string
  | cko of lib * string * int
  | wait of lib * string * int
  ;

fun has(new,j) = false
  | has(add(S,i),j) = if i=j 
			then true
			else has(S,j)
  | has(cko(S,i,m),j) = if i=j
			  then true
			  else has(S,j)
  | has(wait(S,i,m),j) = if i=j
			   then true
			   else has(S,j) ;

fun avail(new,i) = 0
  | avail(add(S,i),j) = if i=j
			  then avail(S,j)+1
			  else avail(S,j)
  | avail(cko(S,i,m),j) = if i=j
			    then avail(S,j)-1
			    else avail(S,j)
  | avail(wait(S,i,m),j) = if i=j
			     then 0
			     else avail(S,j) ;
			    
fun num(new,i) = 0
  | num(add(S,i),j) = if i=j
			then num(S,j)+1
			else num(S,j)
  | num(cko(S,i,m),j) = num(S,j)
  | num(wait(S,i,m),j) = num(S,j) ;


exception remCheckedOut;
exception remNewLib;

fun remove(new,i) = raise remNewLib
  | remove(add(S,i),j) = if i=j
			then remove(S,j)
			else add(remove(S,j),i)
  | remove(cko(S,i,m),j) = if i=j
			  then raise remCheckedOut
			  else cko(remove(S,j),i,m)
  | remove(wait(S,i,m),j) = wait(remove(S,j),i,m) ;


(* functions used for managing wait list *)
exception topwaitNewLib;

fun topwait(new,i) = raise topwaitNewLib
  | topwait(add(S,i),j) = topwait(S,j)
  | topwait(cko(S,i,m),j) = topwait (S,j)
  | topwait(wait(S,i,m),j) = topwait(S,j) ;


fun numWList(new,i)=0
  | numWList(add(S,i),j) = if i=j
			    then numWList(S,j)-1
			    else numWList(S,j)
  | numWList(cko(S,i,m),j) = numWList(S,j)
  | numWList(wait(S,i,m),j) = if i=j
				then numWList(S,j)+1
				else numWList(S,j) ;

(* end of functions used for managing wait list *)

exception nahCkoLib;

fun nah(new,i,m) = new
  | nah(add(S,i),j,m) = if i=j
			 then S
			 else add(nah(S,j,m),i)
  | nah(cko(S,i,m),j,n) = if numWList(S,j)>0
			   then raise nahCkoLib
			   else cko(nah(S,j,n),i,m)
  | nah(wait(S,i,m),j,n) = S ;



fun cki(new,i,m) = new
  | cki(add(S,i),j,m) = if numWList(S,j)>0
			 then cko(S,j,topwait(S,j))
			 else add(cki(S,j,m),i)
  | cki(cko(S,i,m),j,n) = if numWList(S,j)>0
			   then cko(S,j,topwait(S,j))
			   else add(cki(S,j,m),i)
  | cki(wait(S,i,m),j,n) = if numWList(S,j)>0
			    then cko(S,j,topwait(S,j))
			    else wait(cki(S,j,n),i,m) ;



val lib1 = add(new,"Scarlet Letter");
val lib2 = add(new,"Hardy Boys");
val lib3 = add(new,"Moby Dick");
val lib4 = add(new,"Moby Dick");
val a = num(lib4, "Moby Dick");
val b = has(lib4, "Moby Dick");
val c = has(lib4, "Core Java 2");
val lib5 = cko(lib4, "Moby Dick",5);
val d = avail(lib4,"Moby Dick");
val lib6 = cko(lib4, "Moby Dick",4);
val lib7 = cko(lib4, "Moby Dick",9);
val lib8 = cki(lib4, "Moby Dick",5);