[malekan.cfd]

Dear All,

I need to write an if-statement to check the flow_time status, if it is between a specific times, the analysis must follow some commands. I know the if part:

(if (> (rpgetvar' flow-time) 0.355)
(desired task)

But if-else is something unknown for me. I need add an "else if" condition as well. Does anyone has any experience to share?

[obscureed]

The Scheme if syntax is:

(if test true-action false-action)

For example:

(if (> (rpgetvar 'flow-time) 0.355)
  (late-action)
  (early-action))

You are missing a closing parenthesis in your if, and the quote-mark needs to be moved to the right. If you need more than one command in either branch, you must surround them in a begin:

(begin (action1) (action2))

[malekan.cfd]

Thanks for your comment and useful information. But, what about if-else condition, something equivalent to this:

if (flow-time > 0.1 && flow-time< 0.5)
do something
else if flow-time >= 0.5
do something else

Thanks.

[LuckyTran]

The example above already tells you how to do else, notice the false action and (early action) in the examples.

Note that logically else-if only occurs when the previous condition has failed:

But to be more-precise, Scheme goes like

(if test1-expression then1-expression test2-expression then2-expression else-expression)

So to modify the example above, an if else-if else-if else type statement would look like:

(if 
(> (rpgetvar 'flow-time) 0.355) (action1)
(> (rpgetvar 'flow-time) 0.255) (action2)
(> (rpgetvar 'flow-time) 0.155) (action3)
(action4)
)

[obscureed]

Hi LuckyTran,

The example you give might be valid Scheme (I'm not sure), but it is not accepted by Fluent. You are right, though, that a single if...else (as I provided) is enough to build up multiple tests, because the false-action can be another if. For example:

(if (> a b1) (action1)
  (if (> a b2) (action2)
    (if (> a b3) (action3)
      (action_default))))

Fluent accepts another construction instead of if:

(cond (test1 body1)
      (test2 body2)
      ;;; etc
      (else body))

and here each body can be multiple function calls, with no need for (begin ...).

Ed

[malekan.cfd]

Dear Ed and LuckyTran,

Thanks for your comments.

I agree with Ed, I have tried what you suggested LuckyTran before and Fluent gave me an error.

Ed, what you have explanied means that each (test# body#) can represent an if (test#) plus its action (body#), right?

[LuckyTran]

I think you should both read what I have written again

This is not what I wrote.

(if (> a b1) (action1)
  (if (> a b2) (action2)
    (if (> a b3) (action3)
      (action_default))))

Note that I wrote only one "if" and my example, which does not look anything like this.

This is the same as I wrote but with "if" replaced by "cond"

(cond (test1 body1)
      (test2 body2)
      ;;; etc
      (else body))

[obscureed]

Originally Posted by malekan.cfd

Ed, what you have explanied means that each (test# body#) can represent an if (test#) plus its action (body#), right?

Hi Malekan,

You are basically correct, but (as you have probably worked out) it is different from a series of *separate* (if ...) statements, in that only one branch is ever selected. The branches are tested in the order stated (which sounds obvious, but the order of evaluation is not always guaranteed elsewhere in Scheme). Of course, another way to get only one branch selected is with a *nested* set of (if ...) statements, such as the one I mentioned earlier.

We can take LuckyTran's example and rephrase it such that Fluent will accept it:

(cond 
  ((> (rpgetvar 'flow-time) 0.355) (action1))
  ((> (rpgetvar 'flow-time) 0.255) (action2a) (action2b))
  ((> (rpgetvar 'flow-time) 0.155) 0.333)
  (else (action4a) (action4b) (action4c))
  )

If 'flow-time is 0.3550001, for example, then we call (action1) only.

By the way, I slightly regret focussing on a function call such as "(action1)" as the only branch that I mentioned -- a branch can alternatively be a literal value, as in 0.333 above, with no parentheses. (There would be no purpose to this in the example -- it only matters if the result of the (cond ...) function is then used in some way.) For a (cond ...) statement, there can be multiple actions in a body, and the (cond ...) function returns the value returned by the last action in the selected body.

Ed

[malekan.cfd]

Dear Ed and LuckyTran,

Thanks again for your comments.

Last explanation by Ed made everything clear for me. The idea of having multiple actions in the same if-statement is very useful, thanks for sharing.

Regards,
Malekan

[Saman95]

Originally Posted by obscureed

The Scheme if syntax is:

(if test true-action false-action)

For example:

(if (> (rpgetvar 'flow-time) 0.355)
  (late-action)
  (early-action))

You are missing a closing parenthesis in your if, and the quote-mark needs to be moved to the right. If you need more than one command in either branch, you must surround them in a begin:

(begin (action1) (action2))

hello dear

I want to write command that write case and data but I don't know how to write if statement

(if (= (rpgetvar 'variable) 1) (write-case-data "Iteration-%t.cas") (display "not 100s, do nothing\n"))\n

variable is changed in UDF and case & data are saved.

is it true?

[AlexanderZ]

use %rpgetvar macro
for your case

(%rpgetvar 'variable)

best regards