DIRECTORYGlobals,IO,Parse,Rope;ParseImpl: CEDAR PROGRAMIMPORTSIO,RopeEXPORTS Parse =BEGINOPEN Parse, Globals;Args: PUBLIC PROC[line: Rope.ROPE] RETURNS [Arg] =BEGINresult: Arg _ NIL;prev: Arg _ NIL;cur: Arg;stream: IO.STREAM _ NIL;token1, token2: Rope.ROPE;length: INT;stream _ IO.RIS[line];WHILE TRUE DO        ENABLE  IO.EndOfStream => EXIT;token2 _ NIL;[token: token1] _ IO.GetTokenRope[stream, WhiteSpace];IF token1 = NIL THEN LOOP;length _ Rope.Length[token1];IF length >= 2 THENIF (Rope.Fetch[token1, 0] = '-) AND (Rope.Fetch[token1, 1] = '-)THEN EXIT;IF (Rope.Fetch[token1, 0] = '-) AND (length > 2) THENBEGINtoken2 _ Rope.Substr[base: token1, start: 2, len: length-2];token1 _ Rope.Substr[base: token1, start: 0, len: 2];END;cur _ NEW[ArgRec];cur.rope _ token1;IF result = NIL THEN result _ cur;IF prev # NIL THEN prev.next _ cur;prev _ cur;IF token2 # NIL THENBEGINcur _ NEW[ArgRec];cur.rope _ token2;prev.next _ cur;prev _ cur;END;ENDLOOP;RETURN [result];END;Real: PUBLIC PROC[arg: Arg] RETURNS [parseOK: BOOLEAN, val: REAL] =BEGINENABLE ANY => BEGINparseOK _ FALSE;val _ 0.0;CONTINUE;END;IF arg = NIL THEN RETURN [FALSE, 0.0];val _ IO.GetReal[IO.RIS[arg.rope]];RETURN [TRUE, val];END;Int: PUBLIC PROC[arg: Arg] RETURNS [parseOK: BOOLEAN, val: INT] =BEGINENABLE ANY =>BEGINparseOK _ FALSE;val _ 0;CONTINUE;END;IF arg = NIL THEN RETURN [FALSE, 0];val _ IO.GetInt[IO.RIS[arg.rope]];RETURN [TRUE, val];END;Lookup: PUBLIC PROC[rope: Rope.ROPE,table: DESCRIPTOR FOR ARRAY OF Rope.ROPE]RETURNS [index: INT] = TRUSTED BEGINbotIndex: INTEGER _ 0;topIndex: INTEGER _ LENGTH[table] - 1;char: CHAR;FOR i: INTEGER IN [0..1000) DOIF i >= Rope.Length[rope] THENBEGINIF botIndex = topIndex THEN RETURN [botIndex];RETURN [-1];END;char _ Rope.Fetch[rope, i];WHILE TRUE DOIF Rope.Length[table[botIndex]] > i THENIF Rope.Fetch[table[botIndex], i] = char THEN EXIT;IF botIndex = topIndex THEN RETURN [-2];botIndex _ botIndex + 1;ENDLOOP;WHILE TRUE DOIF Rope.Length[table[topIndex]] > i THENIF Rope.Fetch[table[topIndex], i] = char THEN EXIT;IF botIndex = topIndex THEN RETURN [-2];topIndex _ topIndex - 1;ENDLOOP;ENDLOOP;RETURN [-2];END;WhiteSpace: PUBLIC IO.BreakProc =BEGINIF (char = IO.CR) OR (char = IO.TAB) OR (char = IO.LF)OR (char = IO.SP) THEN RETURN [sepr]ELSE RETURN[other];END;END.   Ё  FILE: ParseImpl.mesaLast edited by John Ousterhout, January 24, 1984 1:06 pmChristian LeCocq April 29, 1986 1:08:52 pm PDTTurn the rope into a stream, then strip off the arguments one at a time.Things are a bit tricky if the first letter of the token is "-".  In this case, the argument could be either a switch (like in Unix, remember?), or it could signify the beginning of a comment.  If it's not a comment, make sure that the rope doesn't contain more than one more character, and if it does then chop off the stuff after the first character into a separate token.Generate either one or two Arg objects for the token(s).The search is carried out using two indices into the table. One index marches up from the start of the table, one marches down from the back of the table.  The two indices delimit the entries of the table whose first characters match the part of rope that we've examined (this only works if the table is ordered monotonically).  To do the match, we examine characters of rope one at a time, squeezing the indices together until we've got a match.Move botIndex up until we find a table entry that matches the current character of rope.Move topIndex down until we find a table entry that matches the current character of rope. Э╩├  Ш JЪЬЩЪЬ8Щ8IcodeЩ.ЧJШ Ъ╧k	Ш	JШJЪЭЬШJШJШЧJШ JЪ╧n	ЬЭЬЭШЪЭШJЪЭЬШJШЧJЪЭЬШJШ JЪЭШJЪЭЬШJШ JШJЪ
ЮЬЭЬЭЬЭЬЭЬШ2Ш JЪЭШJЪЬЭЬШJЪЬЭЬШJШ	JЪЬЭЬЭЬЭЬШJЪЬЭЬШJЪЬЭЬШJШ JЪЬHЩHJШ JЪЬ	ЭЬЭЬШЪЭЬЭЬЭЬШJЪЭЬЭЬЭЬШJЪЬ	ЭЬШJЪЬЭЬ"Ш6JЪЭЬ
ЭЬЭЬЭЬШJШ JЪЬЎЩЎJШ JШЪЭЬЭШЪЭЬЭЬШ@JЪЭЬЭЬШ
ЧЧЪЭЬЭЬЭШ5JЪЭШJШ<JШ5JЪЭЬШЧJШ JЪЬ8Щ8JШ JЪЬЭЬ	ШJШJЪЭЬ
ЭЬЭЬШ"JЪЭЬЭЬЭЬШ#JШЪЭЬ
ЭЬЭШJЪЭШJЪЬЭЬ	ШJШJШJШJЪЭЬШЧJЪЭЬШЧJЪЭЬ
ШJЪЭЬШЧJШ JШJЪЮЬЭЬЭЬЭЬЭЬЭЬШCШ JЪЭШЪЭЬЭЬШJЪЭШJЪЬ
ЭЬШJШ
JЪЭЬШ	JЪЭЬШЧJШ JЪ
ЭЬЭЬЭЬЭЬЭЬШ&JЪЬЭЬ	ЭЬЭЬШ#JЪЭЬЭЬШJЪЭЬШЧJШJЪЮЬЭЬЭЬЭЬЭЬЭЬШAШ JЪЭШЪЭЬЭЬШJЪЭШJЪЬ
ЭЬШJШJЪЭЬШ	ЪЭЬШJШ ЧЧJЪ
ЭЬЭЬЭЬЭЬЭЬШ$JЪЬЭЬЭЬЭЬШ"JЪЭЬЭЬШJЪЭЬШЧJШ JШЪЮЬЭЬЭЬЭЬШ$JЪЬЭ
ЬЭЬЭЬЭЬЭЬШ)JЪЭЬ	ЭЬШJШ JЪЭЬЭШJЪЬ
ЭЬШJЪЬ
ЭЬЭЬШ&JЪЬЭЬШJШ JЪЬ╛Щ╛JШ ЪЭЬЭЬЭЬЭШЪЭЬЭШJЪЭШJЪЭЬЭЬЭЬШ.JЪЭЬШJЪЭЬШЧJШJШ JЪЬXЩXJШ ЪЭЬЭЬЭШЪЭЬ"ЭШ(JЪЭЬ'ЭЬЭЬШ3ЧJЪЭЬЭЬЭЬШ(JШJЪЭЬШJШ ЧJЪЬZЩZJШ ЪЭЬЭЬЭШЪЭЬ"ЭШ(JЪЭЬ'ЭЬЭЬШ3ЧJЪЭЬЭЬЭЬШ(JШJЪЭЬШЧJЪЭЬШЧJЪЭЬШJЪЭЬШЧJШ JШЪЮ
ЬЭЬЭЬШ!JЪЭШЪЭЬ	ЭЬЭЬЭЬ	ЭЬЭЬЭЬ	ЭЬЭЬШ6JЪ
ЭЬ	ЭЬЭЬЭЬЭЬШ$JЪЭЬЭЬШЧJЪЭЬШЧJШ JЪЭЬШЧ ЕЧ    	~  1  