
<<ExpressionsImpl.mesa>>
<<Last Edited by: Arnon, July 19, 1985 2:54:46 pm PDT>>
<<>>
DIRECTORY
Rope,
    IO,
    Basics,
    Atom,
    Convert,
AlgebraClasses,
MathConstructors,
Expressions;

ExpressionsImpl: CEDAR PROGRAM
IMPORTS IO, Convert, AlgebraClasses, MathConstructors
EXPORTS Expressions

= BEGIN OPEN Expressions, Convert, AC: AlgebraClasses;
<<Types>>
ExpressionsError: PUBLIC SIGNAL [reason: ATOM _ $Unspecified] = CODE;
    bitsPerWord: CARDINAL = Basics.bitsPerWord;
    CARD: TYPE = LONG CARDINAL;
    ROPE: TYPE = Rope.ROPE;
    STREAM: TYPE = IO.STREAM;
<<Variables>>
ClassPrintName: AC.PrintNameProc = {
RETURN["Expressions"];
};
ClassLegalFirstChar: AC.LegalFirstCharOp = {
    <<SELECT char FROM>>
        <<= '., IN ['0..'9] => RETURN[TRUE];>>
        <<ENDCASE;>>
    RETURN[TRUE];
};
ClassToExpr: AC.ToExprOp = {
    data: ExpressionData _ NARROW[in.data];
RETURN[data];
}; 
ClassZero: AC.NullaryOp = {
RETURN[ MathConstructors.MakeInt["0"] ]
}; 
ClassOne: AC.NullaryOp = {
RETURN[ MathConstructors.MakeInt["1"] ]
}; 
ExpressionClass: AC.StructureClass _ NEW[AC.StructureClassRec _ [
category: field,
printName: ClassPrintName,
    structureEqual: AC.defaultStructureEqualityTest,
characteristic: ClassCharacteristic,

    isElementOf: AC.defaultElementOfProc,

legalFirstChar: ClassLegalFirstChar,
read: Read,
fromRope: FromRope,
toRope: ToRope,
write: Write,
toExpr: ClassToExpr,

    add: Add,
    negate: Negate,
    subtract: Subtract,
    zero: ClassZero,

    multiply: Multiply,
    commutative: TRUE,
    invert: Invert,
    divide: Divide,
    one: ClassOne,

    equal: Equal,

    ordered: TRUE,
    sign: Sign,
    abs: Abs,
    compare: Compare,

    completeField: TRUE,
    realField: TRUE,
    realClosedField: TRUE,
    algebraicallyClosedField: FALSE,

propList: NIL
    ] ];

Expressions: PUBLIC AC.Structure _ NEW[AC.StructureRec _ [
class: ExpressionClass,
instanceData: NIL
    ] ];

    ExpressionOne: Expression _ FromREAL[1.0]; -- do after Expressions set
    ExpressionZero: Expression _ FromREAL[0.0];

<<I/O and Conversion>>
Read: PUBLIC AC.ReadOp ~ {
    RETURN[NEW[AC.ObjectRec _ [
        structure: Expressions,
        data: NEW[REAL  _ IO.GetExpression[in] ]
        ] ] ];
    };
    FromRope: PUBLIC AC.FromRopeOp = {
        stream: IO.STREAM _ IO.RIS[in];
        RETURN[ Read[stream, structure] ];
        };

    ToRope: PUBLIC AC.ToRopeOp = {
        data: ExpressionData _ NARROW[in.data];
        RETURN[ Convert.RopeFromExpression[data^] ];
        };

Write: PUBLIC AC.WriteOp = {
IO.PutRope[ stream, ToRope[in] ]
}; 

    FromREAL: PUBLIC PROC [real: REAL] RETURNS [Expression] = {
        RETURN[NEW[AC.ObjectRec _ [
            structure: Expressions,
            data: NEW[REAL  _ real]
            ] ] ];
        };

    ToREAL: PUBLIC PROC [real: Expression] RETURNS [REAL] = {
        data: ExpressionData _ NARROW[real.data];
        RETURN[data^];
        };
<<Arithmetic>>
Add: PUBLIC AC.BinaryOp ~ {
    firstData: ExpressionData _ NARROW[firstArg.data];
    secondData: ExpressionData _ NARROW[secondArg.data];
    RETURN[NEW[AC.ObjectRec _ [
        structure: Expressions,
        data: NEW[REAL  _ firstData^ + secondData^ ]
        ] ] ];
    };

Negate: PUBLIC AC.UnaryOp ~ {
    data: ExpressionData _ NARROW[arg.data];
    RETURN[NEW[AC.ObjectRec _ [
        structure: Expressions,
        data: NEW[REAL  _ - data^  ]
        ] ] ];
    };

Subtract: PUBLIC AC.BinaryOp ~ {
    firstData: ExpressionData _ NARROW[firstArg.data];
    secondData: ExpressionData _ NARROW[secondArg.data];
    RETURN[NEW[AC.ObjectRec _ [
        structure: Expressions,
        data: NEW[REAL  _ firstData^ - secondData^  ]
        ] ] ];
    };

Multiply: PUBLIC AC.BinaryOp ~ {
    firstData: ExpressionData _ NARROW[firstArg.data];
    secondData: ExpressionData _ NARROW[secondArg.data];
    RETURN[NEW[AC.ObjectRec _ [
        structure: Expressions,
        data: NEW[REAL  _ firstData^ * secondData^  ]
        ] ] ];
    };

Invert: PUBLIC AC.UnaryOp ~ {
    data: ExpressionData _ NARROW[arg.data];
    RETURN[NEW[AC.ObjectRec _ [
        structure: Expressions,
        data: NEW[REAL  _ 1.0 /  data^  ]
        ] ] ];
    };

Divide: PUBLIC AC.BinaryOp ~ {
    firstData: ExpressionData _ NARROW[firstArg.data];
    secondData: ExpressionData _ NARROW[secondArg.data];
    RETURN[NEW[AC.ObjectRec _ [
        structure: Expressions,
        data: NEW[REAL  _ firstData^ / secondData^  ]
        ] ] ];
    };

<<Comparison>>
Sign:  PUBLIC AC.CompareToZeroOp = {
    data: ExpressionData _ NARROW[arg.data];
    SELECT data^ FROM
        < 0.0 => RETURN[less];
        = 0.0 => RETURN[equal];
        ENDCASE => RETURN[greater];
};
<<>>
Abs: PUBLIC AC.UnaryOp ~ {
    data: ExpressionData _ NARROW[arg.data];
    RETURN[NEW[AC.ObjectRec _ [
        structure: Expressions,
        data: NEW[REAL  _ ABS[data^] ]
        ] ] ];
};

Compare: PUBLIC AC.BinaryCompareOp ~ {
    firstData: ExpressionData _ NARROW[firstArg.data];
    secondData: ExpressionData _ NARROW[secondArg.data];
    SELECT firstData^ FROM
        < secondData^ => RETURN[less];
        = secondData^ => RETURN[equal];
        ENDCASE => RETURN[greater];
};

Equal: PUBLIC AC.EqualityOp ~ {
    firstData: ExpressionData _ NARROW[firstArg.data];
    secondData: ExpressionData _ NARROW[secondArg.data];
RETURN[ firstData^ = secondData^]
};


END.