On Wed, 12 Sep 2007, Allin Cottrell wrote: "Gamma" is a rather special case. Of all Greek letters, it's the only one that's more likely to be used to indicate a function than a parameter (or at least 50/50). The solution I have used for years is to use "gama" with 1 "m" for parameters --- which does look ugly, but saves you incidents like this. Or, we could possibly take advantage of gretl being case sensitive and use "Gamma" (capital g) in the example. Riccardo (Jack) Lucchetti Dipartimento di Economia Università Politecnica delle Marche r.lucchetti(a)univpm.it http://www.econ.univpm.it/lucchetti

On Wed, 12 Sep 2007, I wrote: But let's think about this some more. In a language such as C, it's not possible for user-defined variables and built-in functions to share the same name -- because functions _are_ variables (you can pass functions as arguments to other functions, assign functions as members of structures, and so on). In C, you're free to define a variable called, for example, "printf", as in double printf = 2.56; But if you do so, you've lost the well-known standard C library function printf; that variable is over-written. How does this relate to gretl? Well, right now there's no _real_ collision between a variable called "gamma" and the gretl genr function gamma, because functions are _not_ treated as variables in gretl scripting. There's no collision, because when "gamma" serves as the name of a function it must always be in the context of a function call, where the string "gamma" is immediately followed by a left parenthesis. (And left parenthesis immediately following a variable name is a gretl syntax error.) On the one hand, this means that we're quite secure in relaxing the prohibition on user-defined variables with the same name as gretl functions. Gretl can cope just fine with genr gamma = gamma(1.5) On the other hand, we should think twice about being permissive if we reckon we might wish to expand gretl syntax in a C-like direction in future. If we might want to treat functions as variables, we probably shouldn't be permissive. Unless, that is, we want to be as hard-nosed as C itself, and say that if you want to over-write the gamma function with a variable named gamma that's your prerogative, but then you've lost the gamma function. IMO it's not very likely that we'd want to treat gretl functions as variables, but any other thoughts? Allin.