sml,polyml , Check if function is defined in SML


Check if function is defined in SML

Question:

Tag: sml,polyml

Given an SML source file, is it possible to check (using Poly/ML) whether or not a list of function/value names are defined? If so, how?

Alternatively, I've noticed that you can do the following. Suppose we have a source file to be inspected named somefile.sml. Suppose we create the file test.sml, with the following contents:

use "somefile"
f; (* defined in somefile.sml *)
g; (* undefined *)

And then we run:

use "test" handle e as SyntaxError => (print (exnMessage e));

Unfortunately, this only prints out "Static Errors". Is there any way, similar to that described above, to determine (in code) which functions in "test.sml" are not defined?


Answer:

There's probably no way to do this portably but in Poly/ML you can find out whether a value, or anything else, is defined using PolyML.globalNameSpace.

To test for a value (e.g. a function) use

#lookupVal PolyML.globalNameSpace

This takes a name and returns a option type which is SOME if the value has been defined and NONE if it has not. So

#lookupVal PolyML.globalNameSpace "f";

will return

SOME ?

while

#lookupVal PolyML.globalNameSpace "g";

will return NONE.


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