265 lines
7.1 KiB
Plaintext
265 lines
7.1 KiB
Plaintext
BEGIN
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CLASS ENV;
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BEGIN
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CLASS ITEM(N, X); TEXT N; REAL X;
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BEGIN
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REF(ITEM) NEXT; NEXT :- HEAD; HEAD :- THIS ITEM;
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END ITEM;
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REF(ITEM) HEAD;
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REF(ITEM) PROCEDURE LOOKUP(V); TEXT V;
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BEGIN
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REF(ITEM) I; BOOLEAN FOUND; I :- HEAD;
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WHILE NOT FOUND DO
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IF I == NONE OR ELSE I.N = V
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THEN FOUND := TRUE
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ELSE I :- I.NEXT;
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LOOKUP :- I;
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END LOOKUP;
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REF(ENV) PROCEDURE SET(V, X); TEXT V; REAL X;
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BEGIN
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REF(ITEM) I; I :- LOOKUP(V);
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IF I == NONE THEN I :- NEW ITEM(V, X) ELSE I.X := X;
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SET :- THIS ENV;
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END SET;
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REAL PROCEDURE GET(V); TEXT V;
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GET := LOOKUP(V).X;
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END ENV;
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CLASS EXPR(EV); REF(ENV) EV;
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BEGIN
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REAL PROCEDURE POP;
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BEGIN
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IF STACKPOS > 0 THEN
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BEGIN STACKPOS := STACKPOS - 1; POP := STACK(STACKPOS); END;
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END POP;
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PROCEDURE PUSH(NEWTOP); REAL NEWTOP;
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BEGIN
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STACK(STACKPOS) := NEWTOP;
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STACKPOS := STACKPOS + 1;
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END PUSH;
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REAL PROCEDURE CALC(OPERATOR, ERR); CHARACTER OPERATOR; LABEL ERR;
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BEGIN
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REAL X, Y; X := POP; Y := POP;
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IF OPERATOR = '+' THEN PUSH(Y + X)
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ELSE IF OPERATOR = '-' THEN PUSH(Y - X)
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ELSE IF OPERATOR = '*' THEN PUSH(Y * X)
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ELSE IF OPERATOR = '/' THEN BEGIN
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IF X = 0 THEN
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BEGIN
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EVALUATEDERR :- "DIV BY ZERO";
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GOTO ERR;
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END;
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PUSH(Y / X);
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END
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ELSE IF OPERATOR = '^' THEN PUSH(Y ** X)
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ELSE
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BEGIN
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EVALUATEDERR :- "UNKNOWN OPERATOR";
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GOTO ERR;
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END
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END CALC;
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PROCEDURE READCHAR(CH); NAME CH; CHARACTER CH;
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BEGIN
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IF T.MORE THEN CH := T.GETCHAR ELSE CH := EOT;
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END READCHAR;
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PROCEDURE SKIPWHITESPACE(CH); NAME CH; CHARACTER CH;
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BEGIN
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WHILE (CH = SPACE) OR (CH = TAB) OR (CH = CR) OR (CH = LF) DO
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READCHAR(CH);
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END SKIPWHITESPACE;
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PROCEDURE BUSYBOX(OP, ERR); INTEGER OP; LABEL ERR;
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BEGIN
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CHARACTER OPERATOR;
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REAL NUMBR;
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BOOLEAN NEGATIVE;
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SKIPWHITESPACE(CH);
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IF OP = EXPRESSION THEN
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BEGIN
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NEGATIVE := FALSE;
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WHILE (CH = '+') OR (CH = '-') DO
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BEGIN
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IF CH = '-' THEN NEGATIVE := NOT NEGATIVE;
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READCHAR(CH);
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END;
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BUSYBOX(TERM, ERR);
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IF NEGATIVE THEN
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BEGIN
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NUMBR := POP; PUSH(0 - NUMBR);
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END;
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WHILE (CH = '+') OR (CH = '-') DO
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BEGIN
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OPERATOR := CH; READCHAR(CH);
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BUSYBOX(TERM, ERR); CALC(OPERATOR, ERR);
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END;
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END
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ELSE IF OP = TERM THEN
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BEGIN
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BUSYBOX(FACTOR, ERR);
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WHILE (CH = '*') OR (CH = '/') DO
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BEGIN
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OPERATOR := CH; READCHAR(CH);
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BUSYBOX(FACTOR, ERR); CALC(OPERATOR, ERR)
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END
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END
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ELSE IF OP = FACTOR THEN
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BEGIN
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BUSYBOX(POWER, ERR);
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WHILE CH = '^' DO
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BEGIN
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OPERATOR := CH; READCHAR(CH);
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BUSYBOX(POWER, ERR); CALC(OPERATOR, ERR)
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END
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END
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ELSE IF OP = POWER THEN
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BEGIN
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IF (CH = '+') OR (CH = '-') THEN
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BUSYBOX(EXPRESSION, ERR)
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ELSE IF (CH >= '0') AND (CH <= '9') THEN
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BUSYBOX(NUMBER, ERR)
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ELSE IF (CH >= 'A') AND (CH <= 'Z') THEN
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BUSYBOX(VARIABLE, ERR)
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ELSE IF CH = '(' THEN
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BEGIN
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READCHAR(CH);
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BUSYBOX(EXPRESSION, ERR);
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IF CH = ')' THEN READCHAR(CH) ELSE GOTO ERR;
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END
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ELSE GOTO ERR;
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END
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ELSE IF OP = VARIABLE THEN
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BEGIN
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TEXT VARNAM;
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VARNAM :- BLANKS(32);
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WHILE (CH >= 'A') AND (CH <= 'Z')
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OR (CH >= '0') AND (CH <= '9') DO
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BEGIN
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VARNAM.PUTCHAR(CH);
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READCHAR(CH);
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END;
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PUSH(EV.GET(VARNAM.STRIP));
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END
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ELSE IF OP = NUMBER THEN
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BEGIN
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NUMBR := 0;
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WHILE (CH >= '0') AND (CH <= '9') DO
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BEGIN
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NUMBR := 10 * NUMBR + RANK(CH) - RANK('0'); READCHAR(CH);
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END;
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IF CH = '.' THEN
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BEGIN
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REAL FAKTOR;
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READCHAR(CH);
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FAKTOR := 10;
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WHILE (CH >= '0') AND (CH <= '9') DO
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BEGIN
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NUMBR := NUMBR + (RANK(CH) - RANK('0')) / FAKTOR;
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FAKTOR := 10 * FAKTOR;
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READCHAR(CH);
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END;
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END;
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PUSH(NUMBR);
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END;
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SKIPWHITESPACE(CH);
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END BUSYBOX;
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BOOLEAN PROCEDURE EVAL(INP); TEXT INP;
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BEGIN
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EVALUATEDERR :- NOTEXT;
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STACKPOS := 0;
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T :- COPY(INP.STRIP);
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READCHAR(CH);
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BUSYBOX(EXPRESSION, ERRORLABEL);
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IF NOT T.MORE AND STACKPOS = 1 AND CH = EOT THEN
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BEGIN
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EVALUATED := POP;
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EVAL := TRUE;
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GOTO NOERRORLABEL;
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END;
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ERRORLABEL:
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EVAL := FALSE;
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IF EVALUATEDERR = NOTEXT THEN
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EVALUATEDERR :- "INVALID EXPRESSION: " & INP;
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NOERRORLABEL:
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END EVAL;
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REAL PROCEDURE RESULT;
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RESULT := EVALUATED;
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TEXT PROCEDURE ERR;
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ERR :- EVALUATEDERR;
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INTEGER EXPRESSION, TERM, FACTOR, POWER, NUMBER, VARIABLE;
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CHARACTER TAB, LF, CR, SPACE, EOT, CH;
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REAL ARRAY STACK(0:31);
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INTEGER STACKPOS;
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REAL EVALUATED;
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TEXT EVALUATEDERR, T;
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EXPRESSION := 1;
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TERM := 2;
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FACTOR := 3;
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POWER := 4;
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NUMBER := 5;
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VARIABLE := 6;
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TAB := CHAR(9);
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LF := CHAR(10);
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CR := CHAR(13);
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SPACE := CHAR(32);
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EOT := CHAR(0);
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END EXPR;
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REF(EXPR) EXA, EXB;
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EXA :- NEW EXPR(NEW ENV.SET("X", 3));
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EXB :- NEW EXPR(NEW ENV.SET("X", 5));
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IF EXA.EVAL("2 ^ X") THEN
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BEGIN
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IF EXB.EVAL("2 ^ X")
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THEN OUTFIX(EXB.RESULT - EXA.RESULT, 3, 10)
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ELSE OUTTEXT(EXB.ERR)
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END ELSE OUTTEXT(EXA.ERR);
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OUTIMAGE;
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END.
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