Ah, I see! So, its for convenience that the atoms are printed. And the reason `(+ 1 1) was printed was that it was first evaluated to 2, *then* passed to <p>, who only ever saw the atom 2. Thanks Alex.
On Wed, Apr 5, 2017 at 1:36 AM, Alexander Burger <a...@software-lab.de> wrote: > Hi Bruno, > > > I'm going through the picolisp application development tutorial ( > > http://software-lab.de/doc/app.html#tags) and I'm trying this piece of > code > > at the tags section: > > > > : (<div> 'main > > (<h1> NIL "Head") > > (<p> NIL > > (<br> "Line 1") > > "Line" > > (<nbsp>) > > (+ 1 1) ) ) > > <div class="main"><h1>Head</h1> > > <p>Line 1<br/> > > Line </p> > > </div> > > > > That is, the (+ 1 1) part is not evaluated. > > In fact it *is* evaluated, but it does not print anything. > > All those HTML functions are *print* front-ends, which send text to the > current > output channel. > > : (<h1> NIL "Head") > <h1>Head</h1> > > is nothing more than > > : (prinl "<h1>Head</h1>") > <h1>Head</h1> > > just in a more convenient form. > > The nice thing is that these functions may be nested, as can be seen in > your > example (<div> 'main (<h1> NIL "Head") ..). Still they must print > somewhere at > the bottom. > > So the answer to your question is to write > > (ht:Prin (+ 1 1)) > > or just > > (prin (+ 1 1)) > > ('ht:Prin' is recommended for textual data which may contain HTML meta > characters > to properly escape them) > > > Note that - for convenience - *atomic* expressions (like "Head" or "Line" > in > your example) are printed directly, so that it is not necessary to write > > (<h1> NIL (prin "Head")) # Not needed > > This is also mentioned in doc/app.html as > > • If an argument is an atom (a number or a symbol (string)), its value > is > printed immediately. > > • Otherwise (a list), it is evaluated as a Lisp function (typically > some form > of print statement). > > ♪♫ Alex > -- > UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe >
