Using substitution rules to define a function
- To: mathgroup at yoda.physics.unc.edu
- Subject: Using substitution rules to define a function
- From: Jean.Peccoud at imag.fr (Jean Peccoud)
- Date: Mon, 28 Mar 1994 16:33:11 +0200
Dear Mathgroup,
could anybody explain me what happens here ?
Sol is a solution of an equation
In[32]:=
sol
Out[32]=
2 2
2 a + b w + Sqrt[b] w Sqrt[4 a + b w ]
{{x -> ---------------------------------------},
2
2 2
2 a + b w - Sqrt[b] w Sqrt[4 a + b w ]
{x -> ---------------------------------------}}
2
Here I want to define a function of w which returns the first solution.
In[34]:=
invf1[w_]:=sol[[1,1,2]]
invf1[x]
Out[34]=
2 2
2 a + b w + Sqrt[b] w Sqrt[4 a + b w ]
---------------------------------------
2
but when I want to compute the value of this function for x, w remains.
There must be a basic trick that I did not undestand well in using rules or
patterns.
Thank you.
-----------------------------------
Jean Peccoud
TIMC-IMAG
Faculte de medecine de Grenoble
F-38700 La Tronche
France
tel : (33) 76 63 71 85
fax : (33) 76 51 86 67
E-mail : Jean.Peccoud at imag.fr