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SubVec.h

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/*
    File:           SubVec.h

    Function:       Defines a scatter-gather vector, i.e., a subvector of another vector, 
                    or the row, column or diagonal of a matrix.
                    
    Author(s):      Andrew Willmott

    Copyright:      (c) 1995-2000, Andrew Willmott
 */

#ifndef __SubVec__
#define __SubVec__

#include "vl/VL.h"

class TVec;
 
class TSubVec
{
public:

                    TSubVec(Int n, Int span, TVReal data[]);
                    TSubVec(const TSubVec &v);
                    TSubVec(const TVec &v);

    inline Int      Elts() const { return(elts); };

    inline TVReal   &operator [] (Int i);
    inline TVReal   operator [] (Int i) const;

    TSubVec         &operator = (const TSubVec &v);
    TSubVec         &operator = (const TVec &v);
    
    Int             elts;
    Int             span;
    TVReal          *data; 
};

inline TSubVec  sub(const TSubVec &v, Int start, Int length);   
inline TSubVec  first(const TSubVec &v, Int length);    
inline TSubVec  last(const TSubVec &v, Int length);     


// --- SubVec In-Place operators ----------------------------------------------

TSubVec     &operator += (TSubVec &a, const TSubVec &b);
TSubVec     &operator -= (TSubVec &a, const TSubVec &b);
TSubVec     &operator *= (TSubVec &a, const TSubVec &b);
TSubVec     &operator *= (TSubVec &v, TVReal s);
TSubVec     &operator /= (TSubVec &a, const TSubVec &b);
TSubVec     &operator /= (TSubVec &v, TVReal s);


// --- Inlines ----------------------------------------------------------------

inline TVReal &TSubVec::operator [] (Int i)
{
    CheckRange(i, 0, elts, "Vec::[i]");
    
    return(data[i * span]);
}

inline TVReal TSubVec::operator [] (Int i) const
{
    CheckRange(i, 0, elts, "Vec::[i]");

    return(data[i * span]);
}

inline TSubVec sub(const TSubVec &v, Int start, Int length)
{
    Assert(start >= 0 && length > 0 && start + length <= v.Elts(),
        "(sub(Vec)) illegal subset of vector");

    return(TSubVec(length, v.span, v.data + start * v.span));
}

inline TSubVec first(const TSubVec &v, Int length)
{
    Assert(length > 0 && length <= v.Elts(),
        "(first(Vec)) illegal subset of vector");

    return(TSubVec(length, v.span, v.data));
}

inline TSubVec last(const TSubVec &v, Int length)
{
    Assert(length > 0 && length <= v.Elts(),
        "(last(Vec)) illegal subset of vector");

    return(TSubVec(length, v.span, v.data + (v.elts - length) * v.span));
}

#endif

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