IDEA: clear a-z cmd

[compsystems]

Hello sorry for my bad english

One of the problems for students, when a calculator as HP-PRIME or TI-89 stores a-z user variables, is that if one does not delete the variables, the results are evaluated, without showing the general or symbolic solutions.

See publication in the following link http://courses.wccnet.edu/~palay/math179/intslv92.htm

The TI68k have an option to remove the symbolic variables a-z, I think it would be a good option to incorporate it into the HP-PRIME for cas MODE, The RESTART CMD works but deletes all definitions =(, then a single command is required for the alphabetic variables, or expand RESTART CMD, accepting arguments RESTART([arg])

RESTART( "ALL" );
RESTART( "a-z" );








CAS VIEW

PHP Code:

CAS VIEW
CASE 1:  Preassigning values for x,y,z lowercase
x:=5; y:=6; z:=9;
//1.1: solve lowercase & Maximum simplify
solve( x^2*y+z*(-y-1) = 4*(x+z), x ); // returns 
{ (-√(598)+2)/6,  (√(598)+2)/6 }  // OK, As x,y,z have values, solve cmd solve then evaluate
approx(Ans); 
{  −3.742 , 4.409 }  // -> x=4.40 or x=−3.74 // ok

//1.2: SOLVE uppercase
SOLVE( x^2*y+z*(-y-1) = 4*(x+z), x );  or
SOLVE( x^2*y+z*(-y-1) = 4*(x+z), x, 6 );// returns 
4.40900642021 
SOLVE( x^2*y+z*(-y-1) = 4*(x+z), x, -6 );// returns 
−3.742 

CASE 2: Deleting variables x,y,z
purge(x,y,z); 
//2.1: solve lowercase
solve( x^2*y+z*(-y-1) = 4*(x+z), x );  // returns 
{ (√(y^2*z+5*y*z+4)+2)/y,   (-√(y^2*z+5*y*z+4)+2)/y } // Symbolic result for X1/2

{ (√(y^2*z+5*y*z+4)+2)/y, (-(√(y^2*z+5*y*z+4))+2)/y}|({y = 6,z = 9}); returns
{  4.409, −3.742  }


solve( x^2*y+z*(-y-1) = 4*(x+z), y );  // returns 
{(4*x+5*z)/(x^2-z)}// Symbolic result for Y
{(4*x+5*z)/(x^2-z)}|({x = 5,z = 9}); returns {65/16}

//2.2: SOLVE uppercase
SOLVE( x^2*y+z*(-y-1) = 4*(x+z), x, 6 );  returns "Error: Bad Guess(es)" 
SOLVE( x^2*y+z*(-y-1) = 4*(x+z), x, -6 ); returns "Error: Bad Guess(es)"
SOLVE( x^2*y+z*(-y-1) = 4*(x+z), y, -6 ); returns "Error: Bad Guess(es)"

CASE 3:  Non-zero values for X uppercase
X:=5; Y:=6; Z:=9;
//3.1: solve lowercase  
solve( X^2*Y+Z*(-Y-1) = 4*(X+Z), X); // returns 
{ (-√(598)+2)/6,  (√(598)+2)/6 }  // OK, As x,y,z have values, solve cmd solve then evaluate
approx(Ans); 
{  −3.742 , 4.409 }  // -> x=4.40 or x=−3.74 // ok

//3.2: SOLVE uppercase
SOLVE( X^2*Y+Z*(-Y-1) = 4*(X+Z), X);  or
SOLVE( X^2*Y+Z*(-Y-1) = 4*(X+Z), X, 6); // returns 
4.40900642021  
SOLVE( X^2*Y+Z*(-Y-1) = 4*(X+Z), X, -6);// returns 
−3.742  

CASE 4: Restting variables x,y,z
X:=0; Y:=0; Z:=0; 
//4.1: solve lowercase
solve( X^2*Y+Z*(-Y-1) = 4*(X+Z), X); // returns 
{ 0 }

//4.2: SOLVE uppercase
SOLVE( X^2*Y+Z*(-Y-1) = 4*(X+Z), X, 6);  returns
0 


HOME VIEW

PHP Code:

HOME VIEW
SOLVE(Eq, var, guess) // SOLVE CMD for HOME
CASE 5:
X:=5; Y:=6; Z:=9;
SOLVE( X^2*Y+Z*(-Y-1) = 4*(X+Z), X); returns 4.40900642021 
solve( X^2*Y+Z*(-Y-1) = 4*(X+Z), X);  returns {X}

CASE 6: Restting variables x, y, z
X:=0; Y:=0; Z:=0; 
SOLVE( X^2*Y+Z*(-Y-1) = 4*(X+Z), X); returns 4.40900642021
solve( X^2*Y+Z*(-Y-1) = 4*(X+Z), X); returns {X}