TAL Programmer's Guide

Equivalencing Structures
Using Equivalenced Variables
096254 Tandem Computers Incorporated 10–13
Equivalencing Structures to Structure Pointers
If you equivalence an indirect structure to a structure pointer, the indirect structure
behaves exactly like the structure pointer:
ptr to STR1
PTR
STRUCT .str1;
BEGIN
INT a[0:3];
INT b[0:9];
END;
INT .ptr (str1) := @str1;
STRUCT .str2 = ptr;
BEGIN
STRING a2[0:7];
STRING b2[0:19];
END;
ptr to STR2
STR2STR1
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Avoid Mixing Addressing Modes
Do not equivalence an indirect structure to a direct variable, because the implicit
pointer to the indirect structure cannot point to the structure data. Avoid the
following practice:
319
STRUCT dir_str;
BEGIN
STRING a[0:19];
STRING b[0:49];
END;
STRUCT .ind_str = dir_str;
BEGIN
INT a[0:9];
INT b[0:24];
END;
DIR_STR
ptr to IND_STR
IND_STR
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