yacas 1.3.6-2+b1 / usr / share / yacas / scripts / predicates.rep / code.ys

LocalSymbols(p,x)
[
// test for a scalar
Function("IsScalar",{x}) Not(IsList(x));



// test for a vector
Function("IsVector",{x})
   If(IsList(x),
   Length(Select(IsList,x))=0,
   False);

// test for a vector w/ element test p
Function("IsVector",{p,x})
[
   If(IsList(x),
   [
      Local(i,n,result);
      n:=Length(x);
      i:=1;
      result:=True;
      While(i<=n And result)
      [
	 result:=Apply(p,{x[i]});
	 i++;
      ];
      result;
   ],
   False);
];

// test for a matrix (dr)
Function("IsMatrix",{x})
If(IsList(x) And Length(x)>0,
[
   Local(n);
   n:=Length(x);
   If(Length(Select(IsVector,x))=n,
   MapSingle(Length,x)=Length(x[1])+ZeroVector(n),
   False);
],
False);

// test for a matrix w/ element test p (dr)
Function("IsMatrix",{p,x})
If(IsMatrix(x),
[
   Local(i,j,m,n,result);
   m:=Length(x);
   n:=Length(x[1]);
   i:=1;
   result:=True;
   While(i<=m And result)
   [
      j:=1;
      While(j<=n And result)
      [
         result:=Apply(p,{x[i][j]});
         j++;
      ];
      i++;
   ];
   result;
],
False);

/* remove? (dr)
IsSquareMatrix(_x) <--
[
   Local(d);
   d:=Dimensions(x);
   Length(d)=2 And d[1]=d[2];
];
*/

// test for a square matrix (dr)
Function("IsSquareMatrix",{x}) IsMatrix(x) And Length(x)=Length(x[1]);
// test for a square matrix w/ element test p (dr)
Function("IsSquareMatrix",{p,x}) IsMatrix(p,x) And Length(x)=Length(x[1]);

]; // LocalSymbols(p,x)

/* changed definition of IsRational, Nobbi 030529
Function("IsRational",{aLeft}) Type(aLeft) = "/";

Function("IsRationalNumeric",{aLeft})
    Type(aLeft) = "/" And
    IsNumber(aLeft[1]) And
    IsNumber(aLeft[2]);

IsRationalOrNumber(_x) <-- (IsNumber(x) Or IsRationalNumeric(x));

10 # IsRationalOrInteger(x_IsInteger) <-- True;
10 # IsRationalOrInteger(x_IsInteger / y_IsInteger) <-- True;
20 # IsRationalOrInteger(_x) <-- False;

*/

10 # IsRational(x_IsInteger) <-- True;
10 # IsRational(x_IsInteger / y_IsInteger) <-- True;
10 # IsRational(-(x_IsInteger / y_IsInteger)) <-- True;
60000 # IsRational(_x) <-- False;

10 # IsRationalOrNumber(x_IsNumber) <-- True;
10 # IsRationalOrNumber(x_IsNumber / y_IsNumber) <-- True;
10 # IsRationalOrNumber(-(x_IsNumber / y_IsNumber)) <-- True;
60000 # IsRationalOrNumber(_x) <-- False;


IsNegativeNumber(x):= IsNumber(x) And x < 0;
IsNonNegativeNumber(x):= IsNumber(x) And x >= 0;
IsPositiveNumber(x):= IsNumber(x) And x > 0;

IsNegativeInteger(x):= IsInteger(x) And x < 0;
IsNonNegativeInteger(x):= IsInteger(x) And x >= 0;
IsPositiveInteger(x):= IsInteger(x) And x > 0;


/*
10 # IsZero(x_IsNumber) <-- (MathDivide( Round( MathMultiply(x, 10^Builtin'Precision'Get()) ), 10^Builtin'Precision'Get() ) = 0);
10 # IsNotZero(x_IsNumber)       <-- ( RoundTo(x,Builtin'Precision'Get()) != 0);
*/
// these should be calls to MathSign() and the math library should do this. Or it should be just MathEquals(x,0).
// for now, avoid underflow and avoid IsZero(10^(-Builtin'Precision'Get())) returning True.
10 # IsZero(x_IsNumber) <-- ( MathSign(x) = 0 Or MathAbs(x)  < MathPower(10, -Builtin'Precision'Get()));
60000 # IsZero(_x) <-- False;

10 # IsNotZero(x_IsNumber) <-- ( MathAbs(x)  >= MathPower(10, -Builtin'Precision'Get()));
10 # IsNotZero(x_IsInfinity) <-- True;
60000 # IsNotZero(_x) <-- False;

IsNonZeroInteger(x) := (IsInteger(x) And x != 0);

// why do we need this? Why doesn't x=1 not work?
10 # IsOne(x_IsNumber) <-- IsZero(MathSubtract(x,1));
60000 # IsOne(_x) <-- False;

IsEven(n) := IsInteger(n) And ( BitAnd(n,1)  = 0 );
IsOdd(n)  := IsInteger(n) And ( BitAnd(n,1)  = 1 );

IsEvenFunction(f,x):= (f = Eval(Subst(x,-x)f));
IsOddFunction(f,x):= (f = Eval(-Subst(x,-x)f));


10 # IsInfinity(Infinity) <-- True;
10 # IsInfinity(-(_x)) <-- IsInfinity(x);

// This is just one example, we probably need to extend this further to include all
// cases for f*Infinity where f can be guaranteed to not be zero
11 # IsInfinity(Sign(_x)*y_IsInfinity) <-- True;

60000 # IsInfinity(_x) <-- False;

10 # IsConstant(expr_IsAtom) <-- Not IsVariable(expr);

20 # IsConstant(expr_IsFunction) <-- [
    Local(args, a, is'const);

    args := Tail(Listify(expr));

    is'const := True;

    While (args != {} And is'const) [
        a := Head(args);
        args := Tail(args);

        is'const := is'const And IsConstant(a);
    ];

    is'const;
];


Function ("IsBoolean", {x})
	(x=True) Or (x=False) Or IsFunction(x) And Contains({"=", ">", "<", ">=", "<=", "!=", "And", "Not", "Or"}, Type(x));

0 # IsBoolType(True) <-- True;
0 # IsBoolType(False) <-- True;
1 # IsBoolType(_anythingelse) <-- False;

/* See if a number, when evaluated, would be a positive/negative real value */
IsPositiveReal(_r) <--
[
  r:=N(Eval(r));
  (IsNumber(r) And r >= 0);
];
IsNegativeReal(_r) <--
[
  r:=N(Eval(r));
  (IsNumber(r) And r <= 0);
];


/* Predicates on matrices */
IsDiagonal(A_IsMatrix) <--
[
	Local(i,j,m,n,result);
	m:=Length(A);
	n:=Length(A[1]);
	i:=2;
	result:=(m=n);
	While(i<=m And result)
	[
		j:=1;
		While(j<=n And result)
		[
 			result:= (i=j Or A[i][j] = 0);
 			j++;
		];
		i++;
	];
	result;
];
IsUpperTriangular(A_IsMatrix) <--
[
        Local(i,j,m,n,result);
        m:=Length(A);
        n:=Length(A[1]);
        i:=2;
        result:=(m=n);
        While(i<=m And result)
        [
                j:=1;
                While(j<=n And result)
                [
                        result:= (i<=j Or A[i][j] = 0);
                        j++;
                ];
                i++;
        ];
        result;
];
IsLowerTriangular(A_IsMatrix) <-- (IsUpperTriangular(Transpose(A)));
IsSkewSymmetric(A_IsMatrix) <-- (Transpose(A)=(-1*A));
IsHermitian(A_IsMatrix) <-- (Conjugate(Transpose(A))=A);
IsSymmetric(A_IsMatrix) <-- (Transpose(A)=A);
IsOrthogonal(A_IsMatrix) <-- (Transpose(A)*A=Identity(Length(A)));
IsIdempotent(A_IsMatrix) <-- (A^2 = A);
IsUnitary(A_IsMatrix) <-- (Transpose(Conjugate(A))*A = Identity(Length(A)));

IsVariable(_expr) <-- (IsAtom(expr) And Not(expr=Infinity) And Not(expr= -Infinity) And Not(expr=Undefined) And Not(IsNumber(N(Eval(expr)))));

// check that all items in the list are numbers
IsNumericList(_arg'list) <-- IsList(arg'list) And
	("And" @ (MapSingle(Hold({{x},IsNumber(N(Eval(x)))}), arg'list)));

//////////////////////////////////////////////////
/// Predicates HasExpr*, HasFunc*, ListHasFunc
//////////////////////////////////////////////////

/// HasExpr --- test for an expression containing a subexpression
/// for checking dependence on variables, this may be faster than using VarList or IsFreeOf and this also can be used on non-variables, e.g. strings or numbers or other atoms or even on non-atoms
// an expression contains itself -- check early
10 # HasExpr(_expr, _atom) _ Equals(expr, atom) <-- True;
// an atom contains itself
15 # HasExpr(expr_IsAtom, _atom) <-- Equals(expr, atom);
// a list contains an atom if one element contains it
// we test for lists now because lists are also functions
// first take care of the empty list:
19 # HasExpr({}, _atom) <-- False;
20 # HasExpr(expr_IsList, _atom) <-- HasExpr(Head(expr), atom) Or HasExpr(Tail(expr), atom);
// a function contains an atom if one of its arguments contains it
30 # HasExpr(expr_IsFunction, _atom) <-- HasExpr(Tail(Listify(expr)), atom);

/// Same except only look at function arguments for functions in a given list
HasExprSome(_expr, _atom, _look'list) _ Equals(expr, atom) <-- True;
// an atom contains itself
15 # HasExprSome(expr_IsAtom, _atom, _look'list) <-- Equals(expr, atom);
// a list contains an atom if one element contains it
// we test for lists now because lists are also functions
// first take care of the empty list:
19 # HasExprSome({}, _atom, _look'list) <-- False;
20 # HasExprSome(expr_IsList, _atom, _look'list) <-- HasExprSome(Head(expr), atom, look'list) Or HasExprSome(Tail(expr), atom, look'list);
// a function contains an atom if one of its arguments contains it
// first deal with functions that do not belong to the list: return False since we have already checked it at #15
25 # HasExprSome(expr_IsFunction, _atom, _look'list)_(Not Contains(look'list, Atom(Type(expr)))) <-- False;
// a function contains an atom if one of its arguments contains it
30 # HasExprSome(expr_IsFunction, _atom, _look'list) <-- HasExprSome(Tail(Listify(expr)), atom, look'list);

/// HasFunc --- test for an expression containing a function
/// function name given as string.
10 # HasFunc(_expr, string_IsString) <-- HasFunc(expr, Atom(string));
/// function given as atom.
// atom contains no functions
10 # HasFunc(expr_IsAtom, atom_IsAtom) <-- False;
// a list contains the function List so we test it together with functions
// a function contains itself, or maybe an argument contains it
20 # HasFunc(expr_IsFunction, atom_IsAtom) <-- Equals(Head(Listify(expr)), atom) Or ListHasFunc(Tail(Listify(expr)), atom);

/// function name given as string.
10 # HasFuncSome(_expr, string_IsString, _look'list) <-- HasFuncSome(expr, Atom(string), look'list);
/// function given as atom.
// atom contains no functions
10 # HasFuncSome(expr_IsAtom, atom_IsAtom, _look'list) <-- False;
// a list contains the function List so we test it together with functions
// a function contains itself, or maybe an argument contains it

// first deal with functions that do not belong to the list: return top level function
15 # HasFuncSome(expr_IsFunction, atom_IsAtom, _look'list)_(Not Contains(look'list, Atom(Type(expr)))) <-- Equals(Head(Listify(expr)), atom);
// function belongs to the list - check its arguments
20 # HasFuncSome(expr_IsFunction, atom_IsAtom, _look'list) <-- Equals(Head(Listify(expr)), atom) Or ListHasFuncSome(Tail(Listify(expr)), atom, look'list);

/// ListHasFunc --- test for one of the elements of a list to contain a function
/// this is mainly useful to test whether a list has nested lists, i.e. ListHasFunc({1,2,3}, List)=False and ListHasFunc({1,2,{3}}, List)=True.
// need to exclude the List atom itself, so don't use Listify
19 # ListHasFunc({}, _atom) <-- False;
20 # ListHasFunc(expr_IsList, atom_IsAtom) <-- HasFunc(Head(expr), atom) Or ListHasFunc(Tail(expr), atom);

19 # ListHasFuncSome({}, _atom, _look'list) <-- False;
20 # ListHasFuncSome(expr_IsList, atom_IsAtom, _look'list) <-- HasFuncSome(Head(expr), atom, look'list) Or ListHasFuncSome(Tail(expr), atom, look'list);

/// Analyse arithmetic expressions

HasExprArith(expr, atom) := HasExprSome(expr, atom, {Atom("+"), Atom("-"), *, /});
HasFuncArith(expr, atom) := HasFuncSome(expr, atom, {Atom("+"), Atom("-"), *, /});


/// TODO FIXME document this: FloatIsInt returns True if the argument is integer after removing potential trailing 
/// zeroes after the decimal point
// but in fact this should be a call to BigNumber::IsIntValue()
FloatIsInt(_x) <-- 
   [
     x:=N(Eval(x));
     Local(prec,result,n);
     Set(prec,Builtin'Precision'Get());
     If(IsZero(x),Set(n,2),
     If(x>0,
       Set(n,2+MathFloor(N(FastLog(x)/FastLog(10)))),
       Set(n,2+MathFloor(N(FastLog(-x)/FastLog(10))))
       ));
     Builtin'Precision'Set(n+prec);
     Set(result,IsZero(RoundTo(x-Floor(x),prec)) Or IsZero(RoundTo(x-Ceil(x),prec)));
     Builtin'Precision'Set(prec);
     result;
   ];
//