The wiki documentation for assert only shows the statement form. I found that it also works as a function in an expression. In fact it is like the echo function in that is can be followed by an expression as well to give a value. I tried to update the wiki but it doesn't like my IP address. I used it in a function by putting it in a let. I now realise I could just put it anywhere, but why does let allow an expression on its own without an assignment? E.g. this gives no error or warning: let(42); let(1,2,3); gives: WARNING: Ignoring duplicate variable assignment = 2 WARNING: Ignoring duplicate variable assignment = 3 which is puzzling. It behaves as if it assigns to an anonymous variable.

On 22.01.19 23:40, nop head wrote: > The wiki documentation for assert only shows the statement form. I > found that it also works as a function in an expression. In fact it is > like the echo function in that is can be followed by an expression as > well to give a value. Assert is a parser passed. The parser it self is GNU/Bison based. This sometimes leads to very interesting - but also very consistent - consequences. > E.g. this gives no error or warning: > let(42); We can always add a warning, which seams like a sensible thing to do in that case. I will dwell a bit on that and then get to work. > let(1,2,3); gives: > > WARNING: Ignoring duplicate variable assignment = 2 > > WARNING: Ignoring duplicate variable assignment = 3 > > which is puzzling. It behaves as if it assigns to an anonymous variable. > I would not call it anonymous variable, it is really "" as in empty string as the variable name.

Isn't the let thing a syntax error? I.e. the arguments to let should be assignment statements with name = expression, not just an expression. let(a 42), let(a =) and let(=42) are all syntax errors as expected. On Wed, 23 Jan 2019 at 12:15, Michael Frey <michael.frey@gmx.ch> wrote: > On 22.01.19 23:40, nop head wrote: > > The wiki documentation for assert only shows the statement form. I found > that it also works as a function in an expression. In fact it is like the > echo function in that is can be followed by an expression as well to give a > value. > > Assert is a parser passed. The parser it self is GNU/Bison based. This > sometimes leads to very interesting - but also very consistent - > consequences. > > E.g. this gives no error or warning: > let(42); > > We can always add a warning, which seams like a sensible thing to do in > that case. > > I will dwell a bit on that and then get to work. > > let(1,2,3); gives: > > WARNING: Ignoring duplicate variable assignment = 2 > > WARNING: Ignoring duplicate variable assignment = 3 > > which is puzzling. It behaves as if it assigns to an anonymous variable. > > I would not call it anonymous variable, it is really "" as in empty string > as the variable name. > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >