OpenEuphoria

Re: Version 2.1 -- Persistent parameters ?

• Posted by Quality <quality at ANNEX.COM> Jan 16, 1999
• 526 views

From: Greg Phillips <i.shoot at REDNECKS.COM>


> Odd you should mention that, I *just* wrote a function that does
that....and
>allows the choice between truncation and rounding Pi.... ie:  PI(4,0) is
>3.1415, while PI(3,1) is 3.142


What can I say...  Great minds think alike!  

>
>if anyone's interested, I'll post the source
>


By all means please do (if it's not huge).

 =====

Rob:  A feature idea (maybe for a future release, unless you can add it easy
to 2.1)...

I know Euphoria is interpreted but I wonder if it is possible to create
"persistent" function parameters (basically I'm thinking "encapsulated"
global variables). This discussion on PI might be a good way to explain what
I mean...

Assume function PI(SIZE,MODE) -- returns some value of the universal
constant PI.
   -- SIZE [an integer] is the number of significant positions to the right
of the decimal.  (0..MAXPI)
   -- MODE [a boolean] is a flag for truncate -vs- round the result.
(TRUE=ROUND)

Persistence means that whatever values were given to SZIE and MODE last are
"implied" if not explicitly invoked upon a later call. Thus the following
lines of code executed in sequence yield:

PI(5,0)      -- returns {3.14159}
PI(4,1)      -- returns {3.1416}
PI()              -- also returns {3.1416}
PI(4,0)      -- returns {3.1415}
PI()              --  also returns {3.1415}

When a program starts the values of SIZE and MODE are both set to {-1} by
the engine. If the function is invoked in it's "neutral" PI() syntax without
**first** being assigned a specific set of parameters it is an error.

Ideally there might be some way to offer this feature to the programmer, but
it certainly would be a welcome syntax [IMHO] for certain heavily used math
functions.

What do you think?