Mathematica beginner question: Function nesting


by physicsan
Tags: nesting function
physicsan
physicsan is offline
#1
Nov23-11, 09:21 AM
P: 2
Hello,
I'm quite new to Mathematica and stuck at a point, where I have searched for hours to find a solution, but there seems no way out.

Let's say we have two functions,
f1[x_,y_]=x+y
f2[x_,y_]=x*y

How can a build a function f3, which is e.g. the sum of the other functions f1 and f2, i.e. f3[x_, y_]=x+y+x*y, but without copy&paste, but with direct dependency on f1 and f2?

With f3=f1[x,y]+f2[x,y], the functional dependency on x and y is missing. I need a f3, which also has the same input arguments as f1 and f2 (namely x and y).
With f3[x_,y_]==f1[x,y]+f2[x,y] the functional dependency on the parameters is also not working.

Thanks you for your help,
I'm really desperate :(
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phyzguy
phyzguy is offline
#2
Nov23-11, 09:29 AM
P: 2,070
I think that you don't understand the difference between =(immediate assignment), :=(delayed assignment) and == (test for equality). You want to use := in function assignments so that the assignment is not made until you request evaluation. Try the attached notebook - I think it does what you want.
Attached Files
File Type: nb Functions.nb (3.8 KB, 10 views)
physicsan
physicsan is offline
#3
Nov23-11, 04:49 PM
P: 2
Hi,

a thousand thanks! This is exactly what I was looking for! Sorry for my dummy question, it really seems so dummy now :s
Thank you again for your profound and amazingly fast help, you really made my day! :)

phyzguy
phyzguy is offline
#4
Nov23-11, 05:33 PM
P: 2,070

Mathematica beginner question: Function nesting


You're welcome. Glad I could help.


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