.SD;.FLAGS CAPITALIZE
.TITLE <CALC - ^^ARITHMATIC EXPRESION EVALUATOR
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<CALC
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<CALC - ^^ARITHMATIC EXPRESION EVALUATOR
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^^ROUTINE NAME: <CALC\\
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^^PURPOSE:\\ ^TO EVALUAE A GENERAL ARITHMATIC EXPRESSION.  <CALC IS INVOKED BY TYPING
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<CAL ^^LN(10)*44/SQRT(1039)-5.989\\
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 FOR EXAMPLE.  ^THE RESULT OF THE OPERATION
 IS PRINTED
ON THE TERMINAL.  
.PARAGRAPH
 ^CALC CAN ALSO CARRY OUT SEVERAL "CHAIN" CALCULATIONS SINCE <CALC MAINTAINS
 A SYMBOL TABLE .
^THIS IS ACCOMPLISHD BY TYPING <CAL <_<CR>.  <CALC WILL PROMPT FOR THE
EXPRESSION.  THE "CHAINING" IS ACCOMPLISHED THROUGH THE DEFINITIONS OF
SYMBOLS AS IN <FORTRAN ARITHMATIC EXPRESSIONS.
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^^&BINARY FUNCTIONS&\\
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*    MULTIPLICATION
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/    DIVISION
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-    SUBTRACTION
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+    ADDITION
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**   EXPONENTIATION
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^^&RELATIONAL FUNCTIONS&\\
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|	VERTICAL BAR - "^^OR"\\
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_&	LOGICAL ^^"AND"\\
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_\	"OR" (EQUIVALENT TO |)
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_>=	greater than or equal to
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_<_>	Not equal to
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_<=	less than or equal to
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_>	greater than
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_<	less than
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==	is equal to
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=	arithmatic replacement
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^^UNARY FUNCTIONS\\
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^^SQRT\\(x)	square root of x
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^^LN\\(x)	natural log of x
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^^EXP\\(x)	e to the x
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^^NOT\\(x)	the complement of x
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^^ABS\\(x)	the magnitude of x
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^^CONF\\05(N) 95% CONFIDENCE INTERVAL
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^^CONF\\0l(N) 99% CONFIDENCE INTERVAL
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^^BUILT IN CONTANTS\\
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^^PIE\\------3.1415927
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E  ---------2.7182818
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^^true\\ ----1.0
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^^FALSE\\-----0.0
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.SK;.I -10;^^PRECEDENCE OF THE OPERATORS IN ^&CALC\&\\
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1. ^FIRST, ANYTHING ENCLOSED IN PARENTHESES.
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2. ^UNARY OPERATIONS: - (WHEN USED AS "CHANGE SIGN" OR NEGATION), ^^SQRT\\, ^^LN\\,
^^EXP\\, ^^NOT\\, AND ^^ABS\\.
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3. ^EXPONENTIATION HAS THE NEXT PRIORITY DOWN.
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4. ^MULTIPLICATION AND DIVISION.
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5. ^ADDITION AND SUBTRACTION.
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6. ^LOGICAL ^^AND\\ (_&) AND ^^OR\\ (| OR _\).
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7. ^RELATIONAL OPERATIONS.
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8. ^AND LAST, BUT NOT LEAST, ARITHMETIC REPLACEMENT, (=).
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^NOTE -- ^OPERATORS THAT HAVE EQUAL PRECEDENCE, LIKE MULTIPLY AND
DIVIDE, ARE PROCESSED FROM LEFT TO RIGHT.
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^^SPECIAL OPERATIORS IN ^&CALC\&\\
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^BECAUSE ARITHMETIC EXPRESSIONS IN CALC ARE TREATED TOTALLY AS EXPRESSIONS
INVOLVING \&REAL\& NUMBERS, THE MEANING OF SOME OF THE OPERATORS NEEDS
A LITTLE EXPLANATION.
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^^LOGICAL VALUES\\
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^THE LOGIC VALUE ^^TRUE\\ IS REPRESENTED BY A REAL VALUE 1.0, AND ^^FALSE\\
IS REPRESENTED BY 0.0.  ^HOWEVER, WHEN YOU PERFORM A LOGICAL OPERATION,
ANY OTHER NON-ZERO VALUE IS ALSO CONSIDERED TO BE "^^TRUE\\".
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^^LOGICAL OPERATIONS\\
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^IN THE EXPRESSION ^^A_&B\\ THE ^^AND\\ SYMBOL MEANS RETURN THE VALUE OF
^B IF ^A IS NON ZERO, OTHERWISE RETURN ZERO.  ^THE REASON FOR THIS CHOICE WAS TO ALLOW "^^IF
STATEMENT\\" LIKE EXPRESSIONS IN ^^CALC\\. ^ALSO, IF YOU WERE TO TRY ALL 
COMBINATIONS OF LOGICAL INPUTS TO THE EXPRESSION, YOU WOULD FIND THAT IT DOES
GIVE THE CORRECT LOGICAL RESULT.
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^IN THE EXPRESSION ^A_\^B (OR ^A|^B), THE ^^OR\\ SYMBOL MEANS TO RETURN ^A IF
^B IS ZERO, OR ^B IF ^A IS ZERO.  ^IF BOTH ARE NON-ZERO (^^TRUE\\), THE
VALUE OF ^A IS RETURNED.
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^^RELATIONAL OPERATIONS\\
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^THE RELATIONAL OPERATIONS WILL SIMPLY RETURN A ^^TRUE\\ IF THE EXPRESSION IS
CORRECT, AND A FALSE IF IT IS NOT.  ^THE ONLY PITFALL TO LOOK OUT FOR IS
TO MAKE SURE YOU USE "==" WHEN YOU MEAN "IS EQUAL TO" AND NOT "=", WHICH MEANS
"IS REPLACED BY".
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^^UNARY OPERATIONS\\
^ALL UNARY OPERATONS EXCEPT NEGATION (-) REQUIRE PARENTHESES AROUND THEIR ARGUMENT.
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^HERE IS AN EXPRESSION THAT USES ALL THE SPECIAL FEATURES OF ^^CALC\\, AND
AN EXPLANATION OF WHAT THE EXPRESSION WILL DO:
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^^((A=BLANKS==0)_&REALS/BLANKS)|(NOT(A)_&REALS)\\
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^THE EXPRESSION ^^BLANKS==0\\ IS EVALUATED FIRST AND THE RESULT, EITHER
^^TRUE\\ OR ^^FALSE\\ IS STORED IN ^A FOR USE LATER.  ^IF THE RESULT
WAS ^^TRUE\\, THEN THE EXPRESSION ^^REALS/BLANKS\\ IS EVALUATED TO GIVE THE
RESULT OF THE WHOLE EXPRESSION.  ^WHEN THE RESULT IN ^A IS ^^FALSE\\, (AND
OF COURSE ^^NOT(A)\\ IS ^^TRUE\\), THE RESULT OF THE WHOLE EXPRESSION
BECOMES JUST ^^REALS\\.
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^^ROUTINES USED:\\ ^THE ARITHMATIC PACKAGE
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^^EXAMPLE:\\ ^^CAL 3+6
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THE RESULT IS       9.0
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>
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^^AUTHOR:\\ ^JACK ^MARTINELLI
<CETUS <CORP.
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^^WRITTEN:\\ ^JULY 1978
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^^SOURCE LANGUAGE:\\ <FLEX
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^^OBJECT MODULE NAME:\\ <CALC
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