pTAL Conversion Guide

Pointers

pTAL Conversion Guide—527302-002

10-33

Pointer Arithmetic

Example Revisited

The following example was given earlier in this topic:

INT .x; ! Pointer

@x := (@x + 3) / 4 * 4; ! Round @x up to next 4-byte address

As noted, this example works correctly in TAL but not in pTAL because pTAL does not

support multiplication or division on address types. Figure 10-4 on page 10-33

illustrates this case.

Example 10-14. Abbreviated Comparisons

TAL

INT .p;

INT .EXT .q;

IF @p THEN ... ! Equivalent to "IF @p <> 0 THEN ..."

IF NOT @p THEN ... ! Equivalent to "IF @p = 0 THEN ..."

IF @q <> 0D THEN ... ! Must specify 0D

IF NOT @q = 0D THEN ... ! Must specify 0D

pTAL

INT .p;

INT .EXT q;

IF @p THEN ... ! Equivalent to "IF @p <> 0 THEN ..."

IF NOT @p THEN ... ! Equivalent to "IF @p = 0 THEN ..."

IF @q THEN ... ! Equivalent to "IF @q <> 0D THEN ..."

IF NOT @q THEN ... ! Equivalent to "IF @q = 0D THEN ..."

Figure 10-4. An Invalid Arithmetic Expression in pTAL

@x := (@x + 3) / 4 * 4;

WADDR

INT

Error

VST030.vsd