Re: What Do FL and EXP Mean in Csound Source Code?

Re: What Do FL and EXP Mean in Csound Source Code?

Date

2017-03-19 04:08

From

Partev Barr Sarkissian

Subject

Re: What Do FL and EXP Mean in Csound Source Code?

That makes sense. "FL tends to point to Floats in most of what I've seen.
This example is single precision?

Isn't e^x :: Euler to the "x" power exponent?
And x^(n) would be the base of "x" to the power exponent "n"-some number?

-PBS

===============================================

--- jpff@CODEMIST.CO.UK wrote:

From: John ff <jpff@CODEMIST.CO.UK>
To: CSOUND@LISTSERV.HEANET.IE
Subject: Re: [Csnd] What Do FL and EXP Mean in Csound Source Code?
Date: Wed, 15 Mar 2017 12:05:03 +0000

EXP is a macro that deals with float/double option. FL is similar for constants.

Sent from TypeApp

On 15 Mar 2017, at 05:52, Nikhil Singh <nsingh1@BERKLEE.EDU> wrote:

I could be wrong but I think you're right - looks like EXP is #defined as exp (which is e^x), and FL is #defined as x##f which essentially concatenates the 'f' token with the number, making it a float rather than implicitly a double (the equivalent of 3.3f for example, rather than 3.3).

On Tue, Mar 14, 2017 at 10:36 PM, Emmett Palaima <epalaima@berklee.edu> wrote:

Hi I am looking at the source code for the follow2 opcode in Csound: https://github.com/csound/csound/blob/2ef3d7cd3f0a910122a61bf45d7fd7b1f22724fa/Opcodes/follow.c, and am finding the following lines used to set the attack parameter somewhat confusing:

if (p->lastatt!=*p->attack) {

p->lastatt = *p->attack;

if (p->lastatt<=FL(0.0))

ga = p->ga = EXP(- FL(69.0775527898)*csound->onedsr);

// EXP(-FL(10000.0)*csound->onedsr);

else

ga = p->ga = EXP(- FL(6.90775527898)/(CS_ESR* p->lastatt));

//EXP(-FL(1.0)/(CS_ESR* p->lastatt));

}

What do EXP and FL mean in this context? I am thinking EXP(x) is e^x, is this correct? What is FL doing (maybe casting as float?)?

Lastly, I assume CS_ESR and *csound->onedsr are accessing the sample rate, but what is the purpose of using these two different methods to get it?

Thanks!

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Date	2017-03-19 19:57
From	jpff
Subject	Re: What Do FL and EXP Mean in Csound Source Code?
	On Sat, 18 Mar 2017, Partev Barr Sarkissian wrote: > > > That makes sense. "FL tends to point to Floats in most of what I've seen. > This example is single precision? > > Isn't e^x :: Euler to the "x" power exponent? > And x^(n) would be the base of "x" to the power exponent "n"-some number? > > True but not useful. Te exp function (ad expf) re much more efficient. FL(1.0) expands to 1.0 is USE_DOUBLE or 1.0f if not. Removes a number of compiler warnings and potential type conversions Csound mailing list Csound@listserv.heanet.ie https://listserv.heanet.ie/cgi-bin/wa?A0=CSOUND Send bugs reports to https://github.com/csound/csound/issues Discussions of bugs and features can be posted here