Re: Re: Re: Putting an If in my function

*To*: mathgroup at smc.vnet.net*Subject*: [mg101191] Re: [mg101093] Re: [mg101073] Re: Putting an If in my function*From*: DrMajorBob <btreat1 at austin.rr.com>*Date*: Fri, 26 Jun 2009 06:51:17 -0400 (EDT)*References*: <h1neun$8rk$1@smc.vnet.net> <200906241029.GAA22903@smc.vnet.net>*Reply-to*: drmajorbob at bigfoot.com

Set (=) is evaluated immediately, but the condition (/;g == w) can't be evaluated until g and w are known. Bobby On Wed, 24 Jun 2009 05:29:07 -0500, Porscha Louise McRobbie <pmcrobbi at umich.edu> wrote: > Hi, > > I'm also interested in adding a special case to a function. Using > what's written below works fine: > > myFun[a_, g_, f_, x_, d_, w_] := d + a f x /; g == w > > But why doesn't the same work when the myFun is defined using "=" > instead of":="? i.e., > > myFun[a_, g_, f_, x_, d_, w_] = (d + a f x) /; g == w > ln[5]:=myFun[a, w, f, x, d, w] > Out[5]=d + a f x /; w == w > > Thanks, > Porscha > > > Quoting "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>: > >> Dear lobotomy, >> >> "Nomen est omen", the old Romans used to say. And they were often >> right. >> >> I'm not sure what you are trying to do here, with your function in an >> unneccessary, overly complex, pure function notation. Why not write: >> >> myFun[a_, g_, f_, x_, d_, w_] := d (1 + (E^g - E^w)/f)^(f x) + (a (-1 >> + (1 + (E^g - E^w)/f)^(f x)) f)/( E^g - E^w) >> >> which is much more readable (at least in Mathematica)? >> >> In[31]:= Limit[myFun[a, g, f, x, d, w], g -> w] >> >> Out[31]= d + a f x >> >> You use the undefined 'n' in d + a n. I guess this must be f x... >> >> You can add a definition for myFun for this special case like this (no >> If[ ] necessary): >> >> myFun[a_, g_, f_, x_, d_, w_] := d + a f x /; g == w >> >> In[36]:= myFun[a, w, f, x, d, w] >> >> Out[36]= d + a f x >> >> If you want to use an If in the definition this would be something >> like: >> >> myFun[a_, g_, f_, x_, d_, w_] := If[g===w, d (1 + (E^g - E^w)/f)^(= > f= >> x) >> + (a (-1 + (1 + (E^g - E^w)/f)^(f x)) f)/( E^g - E^w),d + a f x] >> >> Cheers -- Sjoerd >> >> On Jun 22, 10:21 am, Lobotomy <labb... at gmail.com> wrote: >>> Hi, this is my function >>> >>> #5 (1 + ((E^#2 - 1) - (E^#6 - >>> 1))/#3)^(#3*#4) + (#1*((1 + (((E^#2 - 1) - (E^#6 = >> - >>> 1))/#3))^(#3*#4) - >>> 1))/(((E^#2 - 1) - (E^#6 - 1))/#3) &[a, g, f, x, d, w] >>> >>> in the case when w==g the denominator equals zero. >>> >>> in this case i would like to rewrite the formula above to the much >>> simpler >>> d+a*n. How is this done? I've tried >>> >>> If[w == g, % = d + a*n], but this is not working. Another thing is >>> where to put the "If" >> >> >> >> >> > > -- DrMajorBob at bigfoot.com

**References**:**Re: Re: Putting an If in my function***From:*Porscha Louise McRobbie <pmcrobbi@umich.edu>