96 lines
2.5 KiB
ObjectPascal
96 lines
2.5 KiB
ObjectPascal
type
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Expr = class
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end;
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V = auto class(Expr)
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name: string;
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procedure Deconstruct(var name: string);
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begin
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name := Self.name
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end;
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end;
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Cons = auto class(Expr)
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r: real;
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procedure Deconstruct(var r: real);
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begin
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r := Self.r
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end;
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end;
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Add = auto class(Expr)
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left,right: Expr;
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procedure Deconstruct(var l,r: Expr);
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begin
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l := left; r := right;
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end;
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end;
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Mult = auto class(Expr)
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left,right: Expr;
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procedure Deconstruct(var l,r: Expr);
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begin
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l := left; r := right;
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end;
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end;
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Neg = auto class(Expr)
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ex: Expr;
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procedure Deconstruct(var ex: Expr);
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begin
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ex := Self.ex
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end;
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end;
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function NegC(ex: Expr) := new Neg(ex);
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function ConsC(r: real) := new Cons(r);
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function AddC(ex1,ex2: Expr) := new Add(ex1,ex2);
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function MultC(ex1,ex2: Expr) := new Mult(ex1,ex2);
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function VC(name: string) := new V(name);
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function Simplify(e: Expr): Expr; forward;
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function Simplify1(e: Expr): Expr;
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begin
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match e with
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Mult(Cons(c),Cons(c1)): Result := ConsC(c*c1);
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Mult(Cons(c),ex) when c=1: Result := Simplify(ex);
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Mult(Cons(c),ex) when c=0: Result := ConsC(0);
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Add(Cons(c),ex) when c=0: Result := Simplify(ex);
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Add(ex,Cons(c)) when c=0: Result := Simplify(ex);
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Add(Cons(c),Cons(c1)): Result := ConsC(c+c1);
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Add(Cons(c),ex): Result := AddC(ex,ConsC(c)); // константы - в хвосте!
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Mult(Cons(c),ex): Result := MultC(ex,ConsC(c));
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Add(Add(ex,Cons(c)),Cons(c1)): Result := AddC(ex,ConsC(c+c1)); // ассоциативность
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Mult(Mult(ex,Cons(c)),Cons(c1)): Result := MultC(ex,ConsC(c*c1)); // ассоциативность
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Neg(Cons(c)): Result := ConsC(-c);
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else Result := e;
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end;
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end;
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function Simplify(e: Expr): Expr;
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begin
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match e with
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Mult(e1,e2): Result := Simplify1(MultC(Simplify(e1),Simplify(e2)));
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Add(e1,e2): Result := Simplify1(AddC(Simplify(e1),Simplify(e2)));
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Neg(e1): Result := Simplify1(NegC(Simplify(e1)));
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else Result := e;
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end;
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end;
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function Str(e: Expr): string;
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begin
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match e with
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Mult(l,r): Result := Str(l) + ' * ' + Str(r);
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Add(l,r): Result := Str(l) + ' + ' + Str(r);
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Neg(n): Result := '-' + Str(n);
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Cons(c): Result := c.ToString;
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V(x): Result := x;
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end;
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end;
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begin
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// 0 + 1*x + 1 + 0*(2 + a) + 2
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var r: Expr := AddC(ConsC(1),AddC(MultC(ConsC(1),VC('x')),ConsC(1)));
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r := AddC(r,MultC(ConsC(0),AddC(ConsC(2),VC('a'))));
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r := AddC(r,ConsC(2));
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Str(r).Println;
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r := Simplify(r);
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Str(r).Println;
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end. |