pTAL Conversion Guide

Equivalenced Variables

pTAL Conversion Guide—527302-002

12-18

pTAL

pTAL requires .SG (or .SGX) indirection notation for pointers to data in system globals

and for fields within a structure in system globals; therefore, it accepts only the second

pair of declarations.

Using Equivalenced Variables

You can use an equivalenced variable in an expression anywhere an operand is valid.

In pTAL, you can index a variable that participates in an equivalenced declaration—

either as the equivalenced variable or as the previous variable—even if none of the

variables in the equivalenced group specify array bounds.

Example 12-16. .SG Notation in pTAL

STRUCT .SG s = 'SG' + 0;

BEGIN

INT .SG i;

INT(32) .SG j;

STRUCT k;

BEGIN

INT .SG m;

END;

INT n;

END;

Example 12-17. Equivalenced Variables

INT a; ! Simple variable, cannot be indexed

INT b; ! "Previous variable" for next declaration

INT c = b; ! b and c can be indexed

INT d = c; ! c and d can be indexed

c[2] := b[1]; ! OK: b and c appear in an equivalenced

! declaration

d[2] := c[1]; ! OK: c and d appear in an equivalenced

! declaration

d[2] := a; ! OK: d appears in an equivalenced declaration

a[1] := d; ! ERROR: a cannot be indexed