%%% tu1.sm1,  1998, 11/3
%%% A sample program for authors of packages.

%%% global variables for bfunction
%%% bfunction.*
/bfunction.v [(x) (y) (z)] def   %% default value of v (variables).
/bfunction.s (s) def             %% default value of s.
/bfunction.verbose 0 def         

/bfunction {
  /arg1 set
  [/in-bfunction /aa /typev /setarg /f /s /v] pushVariables 
  [(CurrentRingp) (KanGBmessage)] pushEnv  %% push current global environment.
  [

    /aa arg1 def
    aa isArray { } { (array bfunction) message error } ifelse
    /setarg 0 def
    aa { tag } map /typev set
    typev [ StringP ] eq
    {  /f aa 0 get def
       /v bfunction.v def
       /s bfunction.s def
       /setarg 1 def
    } { } ifelse
    typev [StringP StringP] eq
    {  /f aa 0 get def
       /v [ aa 1 get to_records pop ] def
       /s bfunction.s def
       /setarg 1 def
    } { } ifelse
    typev [StringP ArrayP] eq
    {  /f aa 0 get def
       /v aa 1 get def
       /s bfunction.s def
       /setarg 1 def
    } { } ifelse
    setarg { } { (Argument mismatch) message error } ifelse

    [(KanGBmessage) bfunction.verbose] system_variable


    %%% PROGRAM BODY

    /arg1 [f v s] def  
  ] pop
  popEnv
  popVariables
  arg1
} def

%% Auxiliary function for bfunction.
%% bfunction.*
/bfunction.foo1 {

} def


%% Write usages as follows.
[(bfunction)
 [( a bfunction b)
  (array a; poly b;)
  (a :  [f] ;  string f ;)
  (a :  [f v] ; string f,v; )
  (b is the bfunction of the polynomial f given as a string.)
  $Example  [(x^3-y^2) (x,y)] bfunction :: $
 ]
] putUsages
(bfunction ) messagen

;