Using BIF's on D-Specs

You can specify some ILE built-in functions (BIFs) on D-specs, provided the compiler can evaluate all the BIF's parameters at compile time. For example, to define an array that overlays a character string, you can use the code below:
D                 DS
D   string                      10A
D   array                        1A   overlay(string)
D                                     dim(%size(string))

This technique can also be useful when you're initializing variables:
D codes           C                   'VXZF'
D code_ext        C                   2
D attr1           S              1A   inz(%subst(codes:code_ext:1))

You can even nest BIFs in D-specs. For instance, the above example can be rewritten as:
D attr2           S              1A   inz(%subst(codes:code_ext:
D                                               %size(attr2)))

by Hans Boldt (IBM)

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