 
 
 
8.3.5  Defining a function with history
The as_function_of
command creates a function defined by an expression, even if the desired variable
already has a value.
- 
as_function_of takes two arguments:
- 
x, a variable.
- exprvar, another variable containing an expression which
itself may involve x.
 
- as_function_of(exprvar,x)
returns a function defined by the expression that exprvar
contains.
Example
|  | | (a)->{ return(sqrt(1+a^2)); } |  |  |  |  |  |  |  |  |  |  | 
 | 
Remark.
If the variable b has been assigned several times, the first
assignment of b following the last assignment of a
will be used. Moreover, the order used is the order of validation of
the commandlines, which may not be reflected by the Xcas interface if
you reused previous commandlines.
Example
| a:=2:;
 b:=2*a+1:;
 b:=3*a+2:;
 c:=as_function_of(b,a) | 
|  | | (a)->{ return(sqrt(1+a^2)); } |  |  |  |  |  |  |  |  |  |  | 
 | 
So c(x) is equal to 2x+1. But:
| a:=2:;
 b:=2*a+1:;
 a:=2:;
 b:=3*a+2:;
 c:=as_function_of(b,a) | 
|  | | (a)->{ return(sqrt(2+3*a^2)); } |  |  |  |  |  |  |  |  |  |  | 
 | 
So c(x) is equal to 3x+2.
Hence the line where a is defined must be reevaluated before the good
definition of b.
 
 
