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TBLSET.ICN
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1991-07-13
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############################################################################
#
# Name: tblset.icn
#
# Title: Procedures for set-theoretic table manipulation, treating
# tables as set-theoretic functions.
#
# Author: Alan Beale
#
# Date: March 31, 1990
#
############################################################################
#
# These procedures are defined:
#
# pairset(t) Convert the table t to an equivalent set of ordered pairs
#
# domain(t) Return the domain of the function defined by the table t
#
# range(t) Return the range of the function defined by the table t
#
# inverse(t) Return the functional inverse of the function defined
# by the table t
#
# inverse(t,[]) Return the relational inverse of the function defined
# by the table t.
#
# inverse(t, set([])) The same as the previous, except that each
# table member is a set rather than a list.
#
############################################################################
procedure pairset(Table)
return set(sort(Table))
end
procedure domain(Table)
local dom
dom := set([])
every insert(dom, key(Table))
return dom
end
procedure range(Table)
local ran
ran := set([])
every insert(ran, !Table)
return ran
end
procedure inverse(Table, Default)
local inv, delem, relem
inv := table(Default)
every delem := key(Table) do {
if type(Default) == "list" then
if member(inv, relem := Table[delem]) then
put(inv[relem], delem)
else inv[relem] := [delem]
else if type(Default) == "set" then
if member(inv, relem := Table[delem]) then
insert(inv[relem], delem)
else inv[relem] := set([delem])
else inv[Table[delem]] := delem
}
return inv
end