Edit detail for SandBoxNewtonsMethod revision 1 of 2

The following shows Newton's method for numerically solving f(x)=0. It is also shows examples of calling Axiom expressions and Spad functions from Lisp.

First, define Newton's method using the Axiom interpreter:

-- Axiom interpreter function for Newton's algorithm
R ==> Float

I ==> Integer

newton(f:Expression R,x:Symbol,x0:R):R ==
        dfdx:Expression R := D(f,x)
        xt:R := x0
        fxt:R := subst(f,x=xt)
        iterNum:I := 0
        maxIt:I := 100
        repeat
                xt := xt - fxt/subst(dfdx,x=xt)
                fxt := subst(f,x=xt)
                if abs(fxt)<1.0e-10 then return xt
                iterNum:=iterNum+1::I
                if iterNum >= maxIt then
                        error "Maximum iterations exceeded."

   Function declaration newton : (Expression Float,Symbol,Float) ->
      Float has been added to workspace.

newton(x**2-2.0,x,2.0)

Compiling function newton with type (Expression Float,Symbol,Float)
       -> Float

(1)

newton(y**2-2.0,y,2.0)

(2)

newton(x**2-2.0,x,2.0)-sqrt(2.0)

(3)

Second, we can also do this by calling the Newton method implemented in Lisp. We initially define/hack a Spad package which creates a Lisp function from an interpreter expression.

)lisp (defun |lambdaFuncallSpad| (f) (lambda (x) (funcall f x nil)))
)abbrev package MKULF MakeUnaryLispFunction
++ Tools for making compiled lisp functions from top-level expressions
++ Author: Mark Clements 
++ (based on the MakeUnaryCompiledFunction package by Manuel Bronstein)
++ Date Created: 20 April 2008
++ Date Last Updated: 20 April 2008
++ Description: transforms top-level objects into lisp functions.
MakeUnaryLispFunction(S, D, I): Exports == Implementation where
  S: ConvertibleTo InputForm
  D, I: Type

  SY  ==> Symbol
  DI  ==> devaluate(D -> I)$Lisp

  Exports ==> with
    compiledFunction: (S, SY) -> SY
      ++ compiledFunction(expr, x) returns a function lisp{f: D -> I}
      ++ defined by lisp{(defun f (x) expr)}. 
      ++ Function f is compiled and directly
      ++ applicable to objects of type D (in lisp).

  Implementation ==> add
    import MakeFunction(S)

    compiledFunction(e:S, x:SY) ==
      t := [convert([devaluate(D)$Lisp]$List(InputForm))
           ]$List(InputForm)
      lambdaFuncallSpad(compile(function(e, declare DI, x), t))$Lisp

   Compiling FriCAS source code from file 
      /var/zope2/var/LatexWiki/1657093691659194492-25px002.spad using 
      old system compiler.
Value = |lambdaFuncallSpad|
   MKULF abbreviates package MakeUnaryLispFunction 
   processing macro definition SY ==> Symbol 
   processing macro definition DI ==> (elt Lisp devaluate) D -> I 
   processing macro definition Exports ==> -- the constructor category 
   processing macro definition Implementation ==> -- the constructor capsule 
------------------------------------------------------------------------
   initializing NRLIB MKULF for MakeUnaryLispFunction 
   compiling into NRLIB MKULF 
   importing MakeFunction S
   compiling exported compiledFunction : (S,Symbol) -> Symbol
Time: 0.05 SEC.

(time taken in buildFunctor:  0)

;;;     ***       |MakeUnaryLispFunction| REDEFINED

;;;     ***       |MakeUnaryLispFunction| REDEFINED
Time: 0 SEC.

   Cumulative Statistics for Constructor MakeUnaryLispFunction
      Time: 0.05 seconds

   finalizing NRLIB MKULF 
   Processing MakeUnaryLispFunction for Browser database:
--------(compiledFunction (SY S SY))---------
--------constructor---------
------------------------------------------------------------------------
   MakeUnaryLispFunction is now explicitly exposed in frame initial 
   MakeUnaryLispFunction will be automatically loaded when needed from 
      /var/zope2/var/LatexWiki/MKULF.NRLIB/code

Then we can use this in Axiom...

-- define Newton in Lisp

)lisp (defun newton (f dfdx x0 &optional (tol 1.0d-10)) (let ((xt x0) (fxt (funcall f x0))
(maxit 100) (iternum 0)) (loop (setf xt (- xt (/ fxt (funcall dfdx xt)))) (setf fxt (funcall f
xt)) (if (< (abs fxt) tol) (return xt)) (incf iternum) (if (>= iternum maxit) (error
"Maximum iterations exceeded.")))))

Value = NEWTON
-- Spad->Lisp function translation
compiledDF(expr: EXPR FLOAT, x: Symbol):Symbol ==
        compiledFunction(expr,x)$MakeUnaryLispFunction(EXPR FLOAT,DFLOAT,DFLOAT)

   Function declaration compiledDF : (Expression Float,Symbol) ->
      Symbol has been added to workspace.

-- a short function to call the Lisp code
newtonUsingLisp(f:Expression Float,x:Symbol,x0:DFLOAT):DFLOAT ==
        float(NEWTON(compiledDF(f,x),compiledDF(D(f,x),x),x0)$Lisp)

   Function declaration newtonUsingLisp : (Expression Float,Symbol,
      DoubleFloat) -> DoubleFloat has been added to workspace.

newtonUsingLisp(x**2-2.0,x,2.0::SF)-sqrt(2.0::SF)

Compiling function compiledDF with type (Expression Float,Symbol)
       -> Symbol

Compiling function newtonUsingLisp with type (Expression Float,
      Symbol,DoubleFloat) -> DoubleFloat

Compiling function %A with type DoubleFloat -> DoubleFloat

Compiling function %B with type DoubleFloat -> DoubleFloat

(4)

Third, we can call a compiled Spad function in Lisp. Defining some example functions in Spad:

)abbrev package TESTP TestPackage
R ==> DoubleFloat
TestPackage: with
        f:R -> R
        dfdx:R -> R
  == add
        f(x) == x*x - 2.0::R
        dfdx(x) == 2*x

   Compiling FriCAS source code from file 
      /var/zope2/var/LatexWiki/2983317606354902709-25px004.spad using 
      old system compiler.
   TESTP abbreviates package TestPackage 
   processing macro definition R ==> DoubleFloat 

------------------------------------------------------------------------
   initializing NRLIB TESTP for TestPackage 
   compiling into NRLIB TESTP 
   compiling exported f : DoubleFloat -> DoubleFloat
Time: 0.01 SEC.

   compiling exported dfdx : DoubleFloat -> DoubleFloat
Time: 0.01 SEC.

(time taken in buildFunctor:  0)

;;;     ***       |TestPackage| REDEFINED

;;;     ***       |TestPackage| REDEFINED
Time: 0 SEC.

   Cumulative Statistics for Constructor TestPackage
      Time: 0.02 seconds

   finalizing NRLIB TESTP 
   Processing TestPackage for Browser database:
--->-->TestPackage((f (R R))): Not documented!!!!
--->-->TestPackage((dfdx (R R))): Not documented!!!!
--->-->TestPackage(constructor): Not documented!!!!
--->-->TestPackage(): Missing Description
------------------------------------------------------------------------
   TestPackage is now explicitly exposed in frame initial 
   TestPackage will be automatically loaded when needed from 
      /var/zope2/var/LatexWiki/TESTP.NRLIB/code

and then calling those functions in Lisp from Axiom:

)lisp (defun |lispFunctionFromSpad| (f dom args) (let ((spadf (|getFunctionFromDomain| f (list
dom) args))) (lambda (x) (spadcall x spadf))))

Value = |lispFunctionFromSpad|
float(NEWTON(lispFunctionFromSpad(f,'TestPackage,['DoubleFloat])$Lisp,
        lispFunctionFromSpad(dfdx,'TestPackage,['DoubleFloat])$Lisp,2::SF
)$Lisp)-sqrt(2.0::SF)

(5)