#14 If statements with more than two options (like else if)

[Manfred Zindel]

Hello, when using an IF-structure I can easily prepare it for two options using IFELSE or TEST and IFTRUE and IFFALSE. But what when there are three options or more? Will I have to create a complicated cascade of IFs? As I see, there is no CASE or SWITCH-structure. What is the best way to solve the multi-options problem with IF?

[David Costanzo]

I use series of IF statements. This doesn't look clumsy to me unless there's a "default" case.

You could implement your own SWITCH command that takes three inputs. Something like:

TO SWITCH :value :cases :default

Where :cases is a list of lists. Each sublist is a pair: a case value and an instruction list to RUN if :value equals the case value. If none of the sublists match, then RUN :default.

It would be invoked like:

SWITCH :myvariable [
  [A [PRINT "Adenine  ] ]
  [C [PRINT "Cytosine ] ]  
  [G [PRINT "Guanine  ] ]  
  [T [PRINT "Thymine  ] ]
] [ PRINT [Unknown nucleotide] ]

[Manfred Zindel]

This is a very good solution. Once again, it proves to be easy to extend
FMSLogo in an ovious and meaningful way. Thank you.

Dr.-Ing. Manfred Zindel
Diplom-Mathematiker
mz@pbreport.de +49(0)176-34478812
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Am 05.11.2020 um 03:05 schrieb David Costanzo:

I use series of |IF| statements. This doesn't look clumsy to me unless
there's a "default" case.

You could implement your own |SWITCH| command that takes three inputs.
Something like:

|TO SWITCH :value :cases :default|

Where |:cases| is a list of lists. Each sublist is a pair: a case
value and an instruction list to |RUN| if |:value| equals the case
value. If none of the sublists match, then |RUN :default|.

It would be invoked like:

SWITCH :myvariable [
[A [PRINT "Adenine ] ]
[C [PRINT "Cytosine ] ]
[G [PRINT "Guanine ] ]
[T [PRINT "Thymine ] ]
] [ PRINT [Unknown nucleotide] ]

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[support-requests:#14]
https://sourceforge.net/p/fmslogo/support-requests/14/ If statements
with more than two options (like else if)

Status: open
Group: GUI
Created: Wed Nov 04, 2020 03:54 PM UTC by Manfred Zindel
Last Updated: Wed Nov 04, 2020 03:54 PM UTC
Owner: David Costanzo

Hello, when using an IF-structure I can easily prepare it for two
options using IFELSE or TEST and IFTRUE and IFFALSE. But what when
there are three options or more? Will I have to create a complicated
cascade of IFs? As I see, there is no CASE or SWITCH-structure. What
is the best way to solve the multi-options problem with IF?

---

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