Re: Block conditional expressions (was: Scoping of variables in block constructs)

[sfeam <sf...@us...>]

On Sunday, 15 October 2017 10:19:11 Achim Gratz wrote:
> Achim Gratz writes:
> > Ethan A Merritt via gnuplot-beta writes:
> >>> Also, why is there no block "else if" or maybe even "elsif"?
> >>
> >> No particular reason.  
> >> So far as I can see, all it would gain is to reduce the number of 
> >> required curly brackets by one pair.
> >> Is there something more subtle I'm missing?
> >
> > Maybe.  If the conditional expressions themselve need to be nested, you
> > will either end up with unwieldy formatting
> >
> > if (…) {
> > else {
> >   if (…) {
> >   else {
> >    if (…) {
> >    else {
> >     if (…) {
> >     else {
> >       if (…) {
> >       else {
> >         if (…) {
> >
> > or you'll need to explicitly repeat (and revert) the logical expression
> > from the former branches.
> 
[snip] 
> Example for that latter point:
> So with that hypothetical elsif keyword, things would look a lot saner
> and be less error-prone, I think:
> 
> --8<---------------cut here---------------start------------->8---
> if (days <= 1/24.) {
>   set xtics  15/60.
>   set mxtics 3
> } elsif (days <= 4/24.) {
>   set xtics  1
>   set mxtics 12
> } elsif (days <= 2) {
>   set xtics  1
>   set mxtics 4
> } elsif (days <= 2) {
>   set xtics  2
>   set mxtics 8
> } elsif (days <= 6) {
>   set xtics  6
>   set mxtics 12
> } elsif (days <= 13) {
>   set xtics  12
>   set mxtics 12
> } elsif (days <= 27) {
>   set xtics  24
>   set mxtics 8
> } elsif (days <= 41) {
>   set xtics  24
>   set mxtics 4
> } else {
>   set xtics  7*24
>   set mxtics 14
> }
> --8A<---------------cut here---------------end--------------->8---

There are other possibilities using the existing syntax elements.
For example:

do for [i=0:0] {

if (days <= 1/24.) {
  set xtics  15/60.
  set mxtics 3
  break
} 
if (days <= 4/24.) {
  set xtics  1
  set mxtics 12
 break
}
if (days <= 2) {
  set xtics  1
  set mxtics 4
  break
}
if (days <= 2) {
  set xtics  2
  set mxtics 8
  break
} 
if (days <= 6) {
  set xtics  6
  set mxtics 12
  break
} 
if (days <= 13) {
  set xtics  12
  set mxtics 12
  break
} 
if (days <= 27) {
  set xtics  24
  set mxtics 8
  break
} 
if (days <= 41) {
  set xtics  24
  set mxtics 4
  break
}
else {
  set xtics  7*24
  set mxtics 14
  break
}

}

Essentially a switch/case construct.

	Ethan


> Achim.
>