The CST code creates tuples with:

return T[0] = mktuple(G_ELSEQ, alt, phrases, T);

The AST code gets it wrong and returns T[0] which contains nothing sensible.
(It should contain an index to arbitrary user tuples.  Also $$ and $1 $2 etc
yacc-style to be added to takeon?

Aside: still need to put P_xxx in the grammar at index G_x...

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gtoal@linux:~/github/uparse-main$ cat array2d.c
int fred[6][4];
$define fred[a][b] fred[(a)+1][(b)+2]
fred[23][45] = 123;

gtoal@linux:~/github/uparse-main$ gtcpp < array2d.c
#line 1 "<stdin>"
int fred[6][4];

fred[(23)+1][(45)+2] = 123;


Would be helpful to extend it with scopes - $begin/$end as in HAL.
Which would also imply a command to push a definition so that an earlier
one encountered before the last $begin was restored on a $end ...

btw may want to reverse order of indexes because I believe Imp and C
differ as to row/column-major.

C's right-to-left evaluation of parameters is annoying - but I did find
a note by Peter Stephens that Imp's order of evaluation was undefined and
that if you wanted to force an order you should assign each parameter to
a variable in whatever order you wanted before calling the procedure.
So just document and maybe warn rather than implement differently.

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#pragma GCC diagnostic error "-Wuninitialized"
    foo(a);         /* error is given for this one */

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wuninitialized"
    foo(b);         /* no diagnostic for this one */
#pragma GCC diagnostic pop

    foo(c);         /* error is given for this one */
#pragma GCC diagnostic pop 

    foo(d);         /* depends on command line options */

- to allow checks but suppress them for things like << or calculating a hash where
the multiplication is allowed to overflow.  Maybe invoke with a %control?


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