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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.

Example

a:=sin(x)
     
sin
x
          
b:=sqrt(1+a^2)
     
1+sin2x
          
c:=as_function_of(b,a)
     
(a)->{ return(sqrt(1+a^2)); }           
c(x)
     
1+x2
          
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.


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