DIRECTORY   IO USING [STREAM],Rope USING [ROPE];BoolOps: CEDAR DEFINITIONS = BEGINError: ERROR[ec: ErrorCode, msg: Rope.ROPE];ErrorCode: TYPE = {Null, 				-- never raisedInternalError,							-- should never happen, but probably willSyntaxError,								-- input rope was not of proper syntaxUnknownOperator,						-- a bad operator was found in an expression treeBadPointer,								-- expression tree contains a strange pointerTreeIsNil,									-- the passed tree was NIL and shouldn't beEmptyExpression,						-- an expression was found that had no childrenVariableNotAnInput,					-- a variable was used in an equation but is not one of the inputs (raised by SOPToTT)NotSOP,									-- tree is not in SOP formDoubleInputs,							-- two inputs have the same nameTTIsNil,									-- the passed truth table was NIL and shouldn't beUnknownTTBit 							-- strange bit in truth table};Operator: TYPE = {And, Or, Not, None};Tree: TYPE = SubTree;SubTree: TYPE = REF ANY;    -- either points to an 'Expression' or a 'Leaf'.Expression: TYPE = RECORD [op: Operator _ None,children: LIST OF SubTree _ NIL];Leaf: TYPE = RECORD [neg: BOOL _ FALSE,var: ATOM];TruthBit: TYPE = {One, Zero, NC -- NC means no connection --};PTerm: TYPE = RECORD [bits: SEQUENCE size: NAT OF TruthBit];TruthTable: TYPE = REF TruthTableRec;TruthTableRec: TYPE = RECORD [numInputs, numOutputs, numPTerms: INT _ 0,pterms: SEQUENCE size: NAT OF REF PTerm];RopeToTree: PROC [expr: Rope.ROPE] RETURNS [Tree];TreeToRope: PROC [tree: Tree] RETURNS [Rope.ROPE];TreeToSOP: PROC [tree: Tree] RETURNS [Tree];SOPNot: PROC [tree: Tree] RETURNS [Tree];SOPAnd: PROC [tree1, tree2: Tree] RETURNS [Tree];SOPOr: PROC [tree1, tree2: Tree] RETURNS [Tree];SOPOptimize: PROC [equations: LIST OF Tree] RETURNS [LIST OF Tree];SOPToTT: PROC [inputs: LIST OF ATOM, equations: LIST OF Tree] RETURNS [TruthTable];TTToSOP: PROC [tt: TruthTable] RETURNS [LIST OF Tree];TTToStream: PROC [tt: TruthTable, out: IO.STREAM];StreamToTT: PROC [in: IO.STREAM] RETURNS [TruthTable];END.     Ò  File: BoolOps.mesa Copyright c 1984 by Xerox Corporation.  All rights reserved.Created by: Mayo, July 16, 1984 3:34:59 pm PDTLast Edited by: Mayo, July 23, 1984 11:47:23 am PDT-- Operations on boolean equations consisting of named variables and the operators 'AND' and 'OR'.-- all errors return a rope describing the problem, as well as an error code.-- If there are N inputs and M outputs, then the size of a product term is N+M and the first N values list the variables in the pterm and the next M values describe which outputs use this pterm.Any procedure may raise the Error indication.Convert a rope into an expresion tree.Convert an expression tree into a rope.Convert an arbitrary expression tree into sum-of-products (SOP) form.Perform logical operations on SOP trees to produce another SOP tree.Optimize a set of boolean equations that are in SOP form.  Method used is tailored for PLAs.Convert between SOP equations and truth tables.-- SOPToTT eliminates redundant product terms.-- The 'inputs' argument orders the inputs from [0..n) and the 'equations' argument orders the outputs in the same way.Convert between truth tables and a text stream.-- StreamToTT eliminates redundant product terms.Ê…  ˜ šœ™Jšœ
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