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1996-06-01
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---------------------------> Sather 1.1 source file <--------------------------
-- Copyright (C) International Computer Science Institute, 1994. COPYRIGHT --
-- NOTICE: This code is provided "AS IS" WITHOUT ANY WARRANTY and is subject --
-- to the terms of the SATHER LIBRARY GENERAL PUBLIC LICENSE contained in --
-- the file "Doc/License" of the Sather distribution. The license is also --
-- available from ICSI, 1947 Center St., Suite 600, Berkeley CA 94704, USA. --
--------> Please email comments to "sather-bugs@icsi.berkeley.edu". <----------
-- fset.sa: Hash-based sets of objects of type T.
-------------------------------------------------------------------
class ORIG_FSET{T} is
-- Original version of the FSET class. Use FSET instead
-- Hash array based sets of objects of type T requiring writebacks.
--
-- If T is a subtype of $NIL, then `nil' may not be an element,
-- otherwise the type's default value may not be a element.
--
-- If T is a subtype of $IS_EQ, then `is_eq' will be used for
-- element equality (eg. string equality for STR), otherwise
-- object equality is used.
--
-- If T is a subtype of $HASH, then `hash' will be used for the hash
-- value, otherwise the element `id' will be used.
--
-- May be inherited with `elt_eq', `elt_nil', and `elt_hash' redefined
-- to get a different behavior.
--
-- The tables grow by amortized doubling and so require writeback
-- when inserting and deleting elements. We keep down the load
-- factor to cut down on collision snowballing. The simple
-- collision resolution allows us to support deletions, but makes
-- the behavior with poor hash functions quadratic. Puts a
-- sentinel at the end of the table to avoid one check while
-- searching.
include COMPARE{T};
include AREF{T};
private attr hsize:INT; -- Number of stored entries.
private const load_ratio:INT:=4; -- Allow to be at most 1/load_ratio full
-- We can't have an invariant here, because sometimes we want
-- to be able to destroy 'self' for efficiency.
--invariant:BOOL is
-- -- Class invariant.
-- return void(self) or hsize.is_bet(0,asize) end;
create:SAME is return void end;
create(n:INT):SAME
-- Make a table capable of dealing with `n' elements without
-- expansion. You can simply insert into a void table to create
-- one as well. Self may be void (and often is).
pre n>=1 is
return allocate(1.lshift((3*load_ratio*n/4).highest_bit+1)+1)
end;
create(arr: ARRAY{T}): SAME is return create_from(arr) end;
create_from(a: $CONTAINER{T}): SAME is
res: SAME := #(a.size);
loop res := res.insert(a.elt!) end;
return res;
end;
private allocate(n:INT):SAME is
-- Allocate `n' locations (must be power of 2 plus 1) and
-- initialize to `elt_nil'.
r::=new(n);
if ~void(elt_nil) then loop r.aset!(elt_nil) end end;
return r end;
size:INT is
-- Number of entries in the table. Self may be void.
if void(self) then return 0 else return hsize end end;
copy:SAME is
-- A copy of self.
r:SAME; loop r:=r.insert(elt!) end; return r end;
elt!:T is
-- Yield the elements in self in an arbitrary order. Do not insert
-- or delete from self while calling this. Self may be void.
if ~void(self) then
loop r::=aelt!;
if ~is_elt_nil(r) then yield r end end end end;
first_elt:T is
-- The first element in the table, if any, otherwise elt_nil.
if ~void(self) then
loop r::=aelt!;
if ~is_elt_nil(r) then return r end end end;
return elt_nil end;
has(e: T): BOOL is return test(e) end;
test(e:T):BOOL is
-- True if `e' is `elt_eq' to an element contained in self.
-- Self may be void.
if void(self) then return false end;
h::=elt_hash(e).band(asize-2);
loop te::=[h];
if is_elt_nil(te) then break!
elsif elt_eq(te,e) then return true
end;
h:=h+1 end;
if h=asize-1 then -- hit sentinel
h:=0;
loop te::=[h];
if is_elt_nil(te) then break!
elsif elt_eq(te,e) then return true
end;
h:=h+1 end;
assert h/=asize-1 end; -- table mustn't be filled
return false end;
get(e:T):T is
-- If `e' is `elt_eq' to a table entry, return that entry,
-- otherwise return `elt_nil'. Useful when different objects
-- are treated as equal (eg. a table of strings used to get a
-- unique representative for each class of equal strings).
-- Self may be void.
if void(self) then return elt_nil end;
h::=elt_hash(e).band(asize-2);
loop te::=[h];
if is_elt_nil(te) then break!
elsif elt_eq(te,e) then return te
end;
h:=h+1 end;
if h=asize-1 then h:=0; -- hit sentinel
loop te::=[h];
if is_elt_nil(te) then break!
elsif elt_eq(te,e) then return te
end;
h:=h+1 end;
assert h/=asize-1 end; -- table mustn't be filled
return elt_nil end;
private double_size:SAME
-- A new table of twice the size of self with self's entries
-- copied over.
pre ~void(self) is
r::=allocate((asize-1)*2+1);
loop r:=r.insert(elt!) end;
SYS::destroy(self); -- The old set should never be used now.
return r end;
private should_grow:BOOL is
return (hsize+1)*load_ratio>asize;
end;
insert(e:T):SAME is
-- A possibly new table which includes `e'. If an entry
-- is `elt_eq' to `e' then overwrite it with `e'.
-- Usage: `tbl:=tbl.insert(e)'.
-- Creates a new table if void(self).
r::=self;
if void(r) then r:=allocate(5)
elsif should_grow then r:=double_size end;
asz::=r.asize;
orig_h::=r.elt_hash(e).band(asz-2);
h::=orig_h;
loop te::=r[h];
if is_elt_nil(te) then break!
elsif elt_eq(te,e) then r[h]:=e; return r end;
h:=h+1 end;
if h=asz-1 then h:=0; -- hit sentinel
loop te::=r[h];
if is_elt_nil(te) then break!
elsif elt_eq(te,e) then r[h]:=e; return r end;
h:=h+1 end;
assert h/=asz-1 end; -- table mustn't be filled
assert not_too_many(orig_h,h); -- Look for excessive collisions
r[h]:=e; r.hsize:=r.hsize+1; return r end;
private not_too_many(start, finish:INT):BOOL is
-- A function called in an assert to check that really
-- bad hashing isn't happening, which would probably
-- be a performance bug. Since it is in an assert, this
-- isn't called unless checking is on.
if finish>start+50 then
#ERR+"Found a problem: excessive collisions in "
+SYS::str_for_tp(SYS::tp(self))
+", probably\n"
+"due to a bad hash function in the class "
+SYS::str_for_tp(SYS::tp([start]))
+".\n";
t:T;
typecase t
when $STR then
#OUT + "Snowballing values:\n";
loop
i::=start.upto!(finish-1);
e::=[i];
h::=elt_hash(e);
typecase e
when $STR then
#OUT + i
+ '\t' + h.hex_str
+ '\t' + h.band(asize-2)
+ '\t' + e.str.pretty + '\n';
end;
end;
else
end;
return false;
end;
return true;
end;
private halve_size:SAME
-- A new table of half the size of self with self's entries
-- copied over.
pre ~void(self) and hsize<(asize-1)/4 is
r::=allocate((asize-1)/2+1);
loop r:=r.insert(elt!) end;
SYS::destroy(self); -- The old set should never be used now.
return r end;
private should_shrink:BOOL is
return asize>=33 and hsize<(asize-1)/(load_ratio*2);
end;
delete(e:T):SAME is
-- A possibly new table which deletes the element `e' if it
-- is contained in self. Doesn't modify the table if arg
-- is not contained. Usage: `tbl:=tbl.delete(e)'.
-- Self may be void.
if void(self) then return void end;
h::=elt_hash(e).band(asize-2);
loop te::=[h];
if is_elt_nil(te) then return self
elsif elt_eq(te,e) then break! end;
if h=asize-2 then h:=0 else h:=h+1 end end;
[h]:=elt_nil; hsize:=hsize-1; i::=h; -- h is the index of arg
-- Now check the block after h for collisions.
loop
if i=asize-2 then i:=0 else i:=i+1 end;
te::=[i];
if is_elt_nil(te) then break! end;
hsh::=elt_hash(te).band(asize-2);
if hsh<=i then -- block doesn't wrap around
if h<i and h>=hsh then -- hole in way
[h]:=[i]; h:=i; [i]:=elt_nil end
else -- block wraps
if h>=hsh or h<i then -- hole in way
[h]:=[i]; h:=i; [i]:=elt_nil end end end;
if should_shrink then return halve_size
else return self end end;
clear:SAME is
-- Clear out self, return the space if it has 17 or less entries
-- otherwise return void. Self may be void.
if void(self) then return void end;
if asize<=17 then r::=self; r.hsize:=0;
loop r.aset!(elt_nil) end; return r
else return void end end;
is_empty:BOOL is
-- True if the set is empty. Self may be void.
return (void(self)) or (hsize=0) end;
equals(s:$RO_SET{T}):BOOL is
-- True if `s' has the same elements as self. Self may be void.
loop if ~s.has(elt!) then return false end end;
loop if ~has(s.elt!) then return false end end;
return true
end;
is_disjoint_from(s:SAME):BOOL is
-- True if self and `s' have no elements in common.
-- Self may be void.
loop if s.test(elt!) then return false end end;
return true end;
intersects(s:SAME):BOOL is
-- True if self and `s' have elements in common.
-- Self may be void.
return ~is_disjoint_from(s) end;
is_subset(s:SAME):BOOL is
-- True if all elements of self are contained in `s'.
-- Self may be void.
loop if ~s.test(elt!) then return false end end;
return true end;
to_union(s:SAME):SAME is
-- The union of self and `s', modifies self.
-- Self may be void.
r::=self; loop r:=r.insert(s.elt!) end; return r end;
to_intersect(s:SAME):SAME is
-- The intersection of self and `s', modifies self.
-- Self may be void. Can't think of a way to do this
-- in place.
return intersect(s) end;
intersect(s:SAME):SAME is
-- A new set which is the intersection of self and s.
-- Self may be void.
r:SAME;
loop e::=elt!;
if s.test(e) then r:=r.insert(e) end end; return r end;
to_difference(s:SAME):SAME is
-- The difference of self and `s', modifies self.
-- Self may be void.
r::=self; loop r:=r.delete(s.elt!) end; return r end;
difference(s:SAME):SAME is
-- A new set which is the difference between self and `s'.
-- Self may be void.
r:SAME;
loop e::=elt!;
if ~s.test(e) then r:=r.insert(e) end end;
return r end;
to_sym_difference(s:SAME):SAME is
-- The symmetric difference of self and `s', modifies self.
-- Self may be void.
r::=self;
loop e::=s.elt!;
if r.test(e) then r:=r.delete(e)
else r:=r.insert(e) end end;
return r end;
sym_difference(s:SAME):SAME is
-- A new set which is the symmetric difference between self
-- and `s'. Self may be void.
r:SAME;
loop e::=elt!;
if ~s.test(e) then r:=r.insert(e) end end;
loop e::=s.elt!;
if ~test(e) then r:=r.insert(e) end end;
return r end;
map(m:ROUT{T}:T):SAME is
-- A new set whose elements are `m' applied to those of self.
-- Self may be void.
r:SAME; loop r:=r.insert(m.call(elt!)) end; return r end;
filter(t:ROUT{T}:BOOL):SAME is
-- A new set whose elements are those of self which satisfy `t'.
-- Self may be void.
r:SAME;
loop e::=elt!; if t.call(e) then r:=r.insert(e) end end;
return r end;
-- The following routines are provided for conformance with
-- $RO_SET{T}, and are similar to (but have slightly different
-- names from) other routines that FSET provides directly
union(s: SAME): SAME is
-- This is the only one that conflicts with the old FSET
-- naming scheme.
-- Old union function:union(s:SAME):SAME is return copy.to_union(s) end;
return copy.to_union(s)
end;
some(t:ROUT{T}:BOOL):BOOL is
-- True if some element of self satisfies `t'.
-- Self may be void.
loop if t.call(elt!) then return true end end;
return false end;
every(t:ROUT{T}:BOOL):BOOL is
-- True if every element of self satisfies `t'.
-- Self may be void.
loop if ~t.call(elt!) then return false end end;
return true end;
notany(t:ROUT{T}:BOOL):BOOL is
-- True if none of the elements of self satisfies `t'.
-- Self may be void.
loop if t.call(elt!) then return false end end;
return true end;
notevery(t:ROUT{T}:BOOL):BOOL is
-- True if not every element of self satisfies `t'.
-- Self may be void.
loop if ~t.call(elt!) then return true end end;
return false end;
as_array: ARRAY{T} is
res ::= #ARRAY{T}(size);
loop res.set!(elt!) end;
return res;
end;
str: STR is
-- Prints out a string version of the array of the components
-- that are under $STR
res ::= #FSTR("{");
loop e ::= elt!;
typecase e
when $STR then res := res+",".separate!(e.str);
else res := res+",".separate!("unprintable"); end;
end;
res := res + "}";
return(res.str);
end;
end -- class FSET{T}
-------------------------------------------------------------------