[Gretl-devel] changes regarding genr and lists

[Allin Cottrell]

On Sat, 9 Feb 2008, Riccardo (Jack) Lucchetti wrote:

> On Sat, 9 Feb 2008, Sven Schreiber wrote:
> 
> > That's a nice change, thanks. On a related issue, AFAIK matrix assignments
> > always have to start with 'matrix' as well, or is this no longer true?
> 
> It hasn't been true for a while. The "matrix", "scalar" and "series"
> statements are just aliases for "genr"; as such, they can be omitted. However,
> they may be useful to handle potentially ambiguous cases. For example
> 
> genr scx = 0 # generates the scalar 0
> 
> scalar scx = 0 # same as above
> 
> series sex = 0 # generates a series full of 0s
>                # (no pun intended on anyone's private life)
> 
> matrix mx = 0 # generates a 1x1 zero matrix

Jack is quite right.  I'll expand just a little.  In most cases

  genr x = <expression>
  <type> x = <expression>
  x = <expression>

are all equivalent, for <type> = {"scalar", "series", "matrix"}. 
if the variable "x" is being created anew, writing its type 
explicitly is, IMO, a good idea; and (as Jack says) this is 
required if you want x to be of a type other than the default or 
"natural" type that would result from a given <expression> -- for 
example, scalar for <expression> = "0".

If x is already defined, the type specification should be 
redundant; it ought to be picked up by gretl.  Please submit a bug 
report if this doesn't happen correctly.

That leaves the types "list" and "string".  We're working on 
"list"; it's still somewhat special but becoming less so.  As for 
"string", it's currently handled outside of the "genr" apparatus, 
so it's still the case that the "string" type-specifier is needed 
in all string-variable operations that might be confused with 
genr commands.

Allin.