DIRECTORYBasics,ISBinding,ISToken,ISNode,IO USING [STREAM],Rope;ISScan: CEDAR DEFINITIONS= BEGINParseFailureReason: TYPE = {unsupportedConstruct, unexpectedDelimiter, hitEndOfScript, outOfPlaceConstruct, bindingAbsent, bindingWrongType, spare };ParseFailure: SIGNAL [s: ScanHandle, r: ParseFailureReason];ScanState: TYPE = {null, inProgress, complete, failed};ScanStreamFlavor: TYPE = {characters, tokens};bufferBytes: CARDINAL = 4;Buffer: TYPE = PACKED ARRAY [0..bufferBytes) OF Basics.Byte;ScanStream: TYPE = RECORD [name: ATOM _ NIL,pushed: REF ScanStream _ NIL,token: ISToken.TVHandle _ NIL,body: SELECT type: ScanStreamFlavor FROMcharacters => [cstream: IO.STREAM _ NIL,inString: BOOLEAN _ FALSE],tokens => [tokenList: ISToken.TVHandle _ NIL],ENDCASE _ NULL];CharactersScanner: TYPE = REF characters ScanStream;TokensScanner: TYPE = REF tokens ScanStream;ScanObject: TYPE = RECORD [scanState: ScanState _ null,bindingStack: ISBinding.StackHandle,zoneIsScans, stackIsScans: BOOLEAN _ FALSE,family: ATOM _ NIL,stream: REF ScanStream];ScanHandle: TYPE = REF ScanObject;CreateScan: PROCEDURE [base: Rope.ROPE,index: INT,bindingStack: ISBinding.StackHandle _ NIL,family: ATOM _ NIL ] RETURNS [ScanHandle];PushScan: PROCEDURE [ScanHandle, Rope.ROPE, ATOM];PopScan: PROCEDURE [ScanHandle];InitializeScan: PROCEDURE [ScanHandle];InitializeScanThroughCurly: PROCEDURE [ScanHandle];AdvanceScan: PROCEDURE [ScanHandle];CollectNode: PROCEDURE [scan: ScanHandle, parent: ISNode.Handle _ NIL, bound: BOOL _ FALSE]RETURNS [ISToken.NodeTVHandle];END.  j  ISScan.mesaCopyright c 1985 by Xerox Corporation.  All rights reserved.edit by Ayers  23-May-85 18:44:11  Rick Beach, August 1, 1985 3:08:52 pm PDTMKaplan, September 13, 1985 2:33:29 pm PDTThe input stream.  Can be a character stream, in which case chars are collected into tokens by ISScanImpl.TokenFromCharactersStream[],  or a stream of tokens that are picked off, one by one, by ISScanImpl.TokenFromTokensStream[].  When a stream runs out, the current stream becomes the one in the pushed field, from which further tokens come.  This gives an "include" facility:  when you want to splice in a stream, set the input stream to a new one with the splice, its pushed field being the unspliced input stream.allocateWith: ISToken.ISNodeDotHandle,<<addedNode: CONDITION -- for syncing with scanning -->>allocateWith: ISNode.Handle,Advance scan gets a new token into scanHandle.token.  It should be called whenever a token is used up by  the parser.Collect node returns a node parsed from scan.  It assumes that scan has been positioned past the initial leftCurly token.  It does much of the real work of the parser. Ê÷  ˜ codešœ™Kšœ
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