Select subexpression in equation

[Fortin]

The following assigns the textbook<->algebraic toggle code to the Shift-EEX (Sto>) key. The startview switches to the home settings (-2) while the change is made so that the entry line is updated when returning to Home (-1).

KEY KS_Eex()
BEGIN
STARTVIEW(−2,0);
Entry:=IFTE(Entry==0,1,0);
STARTVIEW(−1);
RETURN "";
END;