[Gretl-devel] changes regarding genr and lists

Fairy long, I'm afraid, but probably worth reading if you do a lot of scripting, particularly with lists or matrices. In working on some scripts lately I've been building lists using the syntax list foo = null loop <something> ... list foo += varname ... endloop This works OK, but I kept forgetting to say "list foo += .." rather than just "foo += ...". The result was an "unknown variable in command" error message, which I found confusing at first, then annoying. (Appearing on the left-hand side of a genr-type expression, "foo" was not recognized as the name of anything, unless you prompted gretl to look for lists with the "list" keyword.) So I've made a start on incorporating lists into the genr mechanism more fully. You no longer have to repeat "list" in front of listnames, as above. Once a list is created, you can add to it, subtract from it, or redefine it, just using its name. While working in this area I discovered a bug or two in genr. For example, up till today, if you typed scalar x = 3 4 you'd get a scalar x with value 3 and no error message, despite the syntactically incorrect trailing " 4". No more. Now, one or more spaces between variables or constants in a genr formula (with no intervening operator or punctuation) has a specific meaning, namely, concatenation of list elements. So, the following is OK: list xlist = 1 2 3 xlist += 4 5 6 But "scalar x = 3 4" will produce an error: it's trying to assign a list to a scalar. One side effect is worth noting. According to the manual, the way to create a matrix out of data series is, e.g., matrix m = { x1, x2, x3 } with the names of the series separated by commas. Up till now, however, this would also work: matrix m = { x1 x2 x3 } This was just sloppiness, and it won't work any more. The other bug I found was the possible masking of lists by scalars or series. E.g. list X = x1 x2 x3 X = log(x1) The second command would go through without flagging any error: you'd get a variable named X, but the list named "X" would now be inaccessible. This can't happen any more: open data4-10 list X = 1 2 3 X = log(ENROLL) However, if you replace the third line with list X = log(ENROLL) you get the effect you might expect, namely, replacing the original list with a new one that has one element, l_ENROLL. There are no doubt some new issues introduced by this change that will need to be hashed out. But the warning I gave earlier about the state of CVS related to breakage of previously valid uses of genr, and I believe that problem is now fixed. Allin.