source: libcfa/src/collections/array.hfa@ baad96e

#pragma once

#include <assert.h>


forall( __CFA_tysys_id_only_X & ) struct tag {};
#define ttag(T) ((tag(T)){})
#define ztag(n) ttag(n)


// 
// The `array` macro is the public interface.
// It computes the type of a dense (trivially strided) array.
// All user-declared objects are dense arrays.
//
// The `arpk` (ARray with PacKing info explicit) type is, generally, a slice with _any_ striding.
// This type is meant for internal use.
// CFA programmers should not instantiate it directly, nor access its field.
// CFA programmers should call ?[?] on it.
// Yet user-given `array(stuff)` expands to `arpk(stuff')`.
// The comments here explain the resulting internals.
//
// Just as a plain-C "multidimesional" array is really array-of-array-of-...,
// so does arpk generally show up as arpk-of-arpk-of...
//
// In the example of `array(float, 3, 4, 5) a;`,
// `typeof(a)` is an `arpk` instantiation.
// These comments explain _its_ arguments, i.e. those of the topmost `arpk` level.
//
// [N]    : the number of elements in `a`; 3 in the example
// S      : carries the stride size (distance in bytes between &myA[0] and &myA[1]), in sizeof(S); 
//          same as Timmed when striding is trivial, same as Timmed in the example
// Timmed : (T-immediate) the inner type; conceptually, `typeof(a)` is "arpk of Timmed";
//          array(float, 4, 5) in the example
// Tbase  : (T-base) the deepest element type that is not arpk; float in the example
//
forall( [N], S & | sized(S), Timmed &, Tbase & ) {

    //
    // Single-dim array sruct (with explicit packing and atom)
    //
    struct arpk {
        S strides[N];
    };

    // About the choice of integral types offered as subscript overloads:
    // Intent is to cover these use cases:
    //    a[0]                                                // i : zero_t
    //    a[1]                                                // i : one_t
    //    a[2]                                                // i : int
    //    float foo( ptrdiff_t i ) { return a[i]; }           // i : ptrdiff_t
    //    float foo( size_t i ) { return a[i]; }              // i : size_t
    //    forall( [N] ) ... for( i; N ) { total += a[i]; }    // i : typeof( sizeof(42) )
    //    for( i; 5 ) { total += a[i]; }                      // i : int
    //
    // It gets complicated by:
    // -  CFA does overloading on concrete types, like int and unsigned int, not on typedefed
    //    types like size_t.  So trying to overload on ptrdiff_t vs int works in 64-bit mode
    //    but not in 32-bit mode.
    // -  Given bug of Trac #247, CFA gives sizeof expressions type unsigned long int, when it
    //    should give them type size_t.
    //
    //                          gcc -m32         cfa -m32 given bug         gcc -m64 (and cfa)
    // ptrdiff_t                int              int                        long int
    // size_t                   unsigned int     unsigned int               unsigned long int
    // typeof( sizeof(42) )     unsigned int     unsigned long int          unsigned long int
    // int                      int              int                        int
    //
    // So the solution must support types {zero_t, one_t, int, unsigned int, long int, unsigned long int}
    //
    // The solution cannot rely on implicit conversions (e.g. just have one overload for ptrdiff_t)
    // because assertion satisfaction requires types to match exacly.  Both higher-dimensional
    // subscripting and operations on slices use asserted subscript operators.  The test case
    // array-container/array-sbscr-cases covers the combinations.  Mike beleives that commenting out
    // any of the current overloads leads to one of those cases failing, either on 64- or 32-bit.
    // Mike is open to being shown a smaller set of overloads that still passes the test.

    static inline Timmed & ?[?]( arpk(N, S, Timmed, Tbase) & a, zero_t ) {
        assert( 0 < N );
        return (Timmed &) a.strides[0];
    }

    static inline Timmed & ?[?]( arpk(N, S, Timmed, Tbase) & a, one_t ) {
        assert( 1 < N );
        return (Timmed &) a.strides[1];
    }

    static inline Timmed & ?[?]( arpk(N, S, Timmed, Tbase) & a, int i ) {
        assert( i < N );
        return (Timmed &) a.strides[i];
    }

    static inline const Timmed & ?[?]( const arpk(N, S, Timmed, Tbase) & a, int i ) {
        assert( i < N );
        return (Timmed &) a.strides[i];
    }

    static inline Timmed & ?[?]( arpk(N, S, Timmed, Tbase) & a, unsigned int i ) {
        assert( i < N );
        return (Timmed &) a.strides[i];
    }

    static inline const Timmed & ?[?]( const arpk(N, S, Timmed, Tbase) & a, unsigned int i ) {
        assert( i < N );
        return (Timmed &) a.strides[i];
    }

    static inline Timmed & ?[?]( arpk(N, S, Timmed, Tbase) & a, long int i ) {
        assert( i < N );
        return (Timmed &) a.strides[i];
    }

    static inline const Timmed & ?[?]( const arpk(N, S, Timmed, Tbase) & a, long int i ) {
        assert( i < N );
        return (Timmed &) a.strides[i];
    }

    static inline Timmed & ?[?]( arpk(N, S, Timmed, Tbase) & a, unsigned long int i ) {
        assert( i < N );
        return (Timmed &) a.strides[i];
    }

    static inline const Timmed & ?[?]( const arpk(N, S, Timmed, Tbase) & a, unsigned long int i ) {
        assert( i < N );
        return (Timmed &) a.strides[i];
    }

    static inline size_t ?`len( arpk(N, S, Timmed, Tbase) & a ) {
        return N;
    }

    static inline void __taglen( tag(arpk(N, S, Timmed, Tbase)), tag(N) ) {}
}

// RAII pattern has workarounds for
//  - Trac 226:  Simplest handling would be, require immediate element to be otype, let autogen
//    raii happen.  Performance on even a couple dimensions is unacceptable because of exponential
//    thunk creation: ?{}() needs all four otype funcs from next level, so does ^?{}(), so do the
//    other two.  This solution offers ?{}() that needs only ?{}(), and similar for ^?{}.

forall( [N], S & | sized(S), Timmed &, Tbase & | { void ?{}( Timmed & ); } )
static inline void ?{}( arpk(N, S, Timmed, Tbase) & this ) {    
    void ?{}( S (&)[N] ) {}
    ?{}(this.strides);

    for (i; N) ?{}( (Timmed &) this.strides[i] );
}

forall( [N], S & | sized(S), Timmed &, Tbase & | { void ^?{}( Timmed & ); } )
static inline void ^?{}( arpk(N, S, Timmed, Tbase) & this ) {
    void ^?{}( S (&)[N] ) {}
    ^?{}(this.strides);

    for (i; N ) {
        ^?{}( (Timmed &) this.strides[N-i-1] );
    }
}

//
// Sugar for declaring array structure instances
//

forall( Te * )
static inline Te mkar_( tag(Te) ) {}

forall( [N], ZTags ... , Trslt &, Tatom & | { Trslt mkar_( tag(Tatom), ZTags ); } )
static inline arpk(N, Trslt, Trslt, Tatom) mkar_( tag(Tatom), tag(N), ZTags ) {}

// based on https://stackoverflow.com/questions/1872220/is-it-possible-to-iterate-over-arguments-in-variadic-macros

    // Make a FOREACH macro
    #define FE_0(WHAT)
    #define FE_1(WHAT, X) WHAT(X)
    #define FE_2(WHAT, X, ...) WHAT(X)FE_1(WHAT, __VA_ARGS__)
    #define FE_3(WHAT, X, ...) WHAT(X)FE_2(WHAT, __VA_ARGS__)
    #define FE_4(WHAT, X, ...) WHAT(X)FE_3(WHAT, __VA_ARGS__)
    #define FE_5(WHAT, X, ...) WHAT(X)FE_4(WHAT, __VA_ARGS__)
    //... repeat as needed

    #define GET_MACRO(_0,_1,_2,_3,_4,_5,NAME,...) NAME
    #define FOR_EACH(action,...) \
    GET_MACRO(_0,__VA_ARGS__,FE_5,FE_4,FE_3,FE_2,FE_1,FE_0)(action,__VA_ARGS__)

#define COMMA_ttag(X) , ttag(X)
#define array( TE, ...) typeof( mkar_( ttag(TE)  FOR_EACH( COMMA_ttag, __VA_ARGS__ ) ) )

#define COMMA_ztag(X) , ztag(X)
#define zarray( TE, ...) typeof( mkar_( ttag(TE)  FOR_EACH( COMMA_ztag, __VA_ARGS__ ) ) )

//
// Sugar for multidimensional indexing
//

// Core -[[-,-,-]] operator

#ifdef TRY_BROKEN_DESIRED_MD_SUBSCRIPT

// Desired form.  One definition with recursion on IxBC (worked until Jan 2021, see trac #__TODO__)

forall( TA &, TB &, TC &, IxAB, IxBC ... | { TB & ?[?]( TA &, IxAB ); TC & ?[?]( TB &, IxBC ); } )
static inline TC & ?[?]( TA & this, IxAB ab, IxBC bc ) {
    return this[ab][bc];
}

#else

// Workaround form.  Listing all possibilities up to 4 dims.

forall( TA &, TB &, TC &, IxAB_0, IxBC | { TB & ?[?]( TA &, IxAB_0 ); TC & ?[?]( TB &, IxBC ); } )
static inline TC & ?[?]( TA & this, IxAB_0 ab, IxBC bc ) {
    return this[ab][bc];
}

forall( TA &, TB &, TC &, IxAB_0, IxAB_1, IxBC | { TB & ?[?]( TA &, IxAB_0, IxAB_1 ); TC & ?[?]( TB &, IxBC ); } )
static inline TC & ?[?]( TA & this, IxAB_0 ab0, IxAB_1 ab1, IxBC bc ) {
    return this[[ab0,ab1]][bc];
}

forall( TA &, TB &, TC &, IxAB_0, IxAB_1, IxAB_2, IxBC | { TB & ?[?]( TA &, IxAB_0, IxAB_1, IxAB_2 ); TC & ?[?]( TB &, IxBC ); } )
static inline TC & ?[?]( TA & this, IxAB_0 ab0, IxAB_1 ab1, IxAB_2 ab2, IxBC bc ) {
    return this[[ab0,ab1,ab2]][bc];
}

#endif

// Available for users to work around Trac #265
// If `a[...0...]` isn't working, try `a[...ix0...]` instead.

#define ix0 ((ptrdiff_t)0)



//
// Rotation
//

// Base
forall( [Nq], Sq & | sized(Sq), Tbase & )
static inline tag(arpk(Nq, Sq, Tbase, Tbase)) enq_( tag(Tbase), tag(Nq), tag(Sq), tag(Tbase) ) {
    tag(arpk(Nq, Sq, Tbase, Tbase)) ret;
    return ret;
}

// Rec
forall( [Nq], Sq & | sized(Sq), [N], S & | sized(S), recq &, recr &, Tbase & | { tag(recr) enq_( tag(Tbase), tag(Nq), tag(Sq), tag(recq) ); } )
static inline tag(arpk(N, S, recr, Tbase)) enq_( tag(Tbase), tag(Nq), tag(Sq), tag(arpk(N, S, recq, Tbase)) ) {
    tag(arpk(N, S, recr, Tbase)) ret;
    return ret;
}

// Wrapper
extern struct all_t {} all;
forall( [N], S & | sized(S), Te &, result &, Tbase & | { tag(result) enq_( tag(Tbase), tag(N), tag(S), tag(Te) ); } )
static inline result & ?[?]( arpk(N, S, Te, Tbase) & this, all_t ) {
    return (result&) this;
}

//
// Trait of array or slice
//

// desired:
// forall(A &, Tv &, [N])
// trait ar {
//     Tv& ?[?]( A&, zero_t );
//     Tv& ?[?]( A&, one_t  );
//     Tv& ?[?]( A&, int    );
//                   ...
//     size_t ?`len( A& );
//     void __taglen( tag(C), tag(N) );
// };

// working around N's not being accepted as arguments to traits

#define ar(A, Tv, N) {                 \
    Tv& ?[?]( A&, zero_t );            \
    Tv& ?[?]( A&, one_t );             \
    Tv& ?[?]( A&, int );               \
    Tv& ?[?]( A&, unsigned int );      \
    Tv& ?[?]( A&, long int );          \
    Tv& ?[?]( A&, unsigned long int ); \
    size_t ?`len( A& );                \
    void __taglen( tag(A), tag(N) );   \
}