What is the difference between ? Definition and ?? Information?
If I define two functions for the same symbol
f[x_] := Cos[x] f[b_, c_] := Sin[b c] I get the same result for ?f and ??f
I've read the documentation, but it's not giving me a real sense of the difference. Are there different use cases? Can I always use one of these (? or ??) and ignore the other?
ps. Which tags are appropriate for this question?
Actually, while the input escape ?? is shorthand for Information, ? is not a shorthand for Definition (though ? might use Definition). Basically, if there is a usage message defined, ? returns that, if not, it returns definitions. Information and ?? always return everything accessible. Compare:
In[25]:= f[x_] := Cos[x] f[b_, c_] := Sin[b c] f::usage = "blahblah"; Definition@f f[x_] := Cos[x] f[b_, c_] := Sin[b c]
?f (* prints usage message if exists, Definitions[f] otherwise *) blahblah
Information@f (* same as ??f *) blahblah f[x_]:=Cos[x] f[b_,c_]:=Sin[b c]
According to the documentation under Document Constructs:
Of course, any definition is only printed if the symbol is not ReadProtected. Information itself is ReadProtected, hence only attributes and options are listed:
Definition@Information Attributes[Information] = {HoldAll, Protected, ReadProtected} Options[Information] = {LongForm -> True}
Compare the above to the extensive output produced by PrintDefinitions, that delves deep into the symbol's definition (large output is omitted):
Needs["GeneralUtilities`"]; PrintDefinitions@Information Furthermore, you can abuse the ? operator to ask about multiple functions:
?*Chart 
?...is the same asInformation[..., LongForm -> False]and different fromDefinition. $\endgroup$