HP 50g Graphing Calculator - Manual (Page 642)

Page 20-3
To activate any of those functions you simply need to enter the function
argument (a number), and then press the corresponding soft menu key.
In ALG mode, the list to be entered as argument of function TMENU or MENU is
more complicated:
{{“exp”,”EXP(“},{“ln”,”LN(“},{“Gamma”,”GAMMA(“},{“!”,”!(“}}
The reason for this is that, in RPN mode, the command names are both soft
menu labels and commands. In ALG mode, the command names will produce
no action since ALG functions must be followed by parentheses and arguments.
In the list shown above (for the ALG mode), within each sub-list you have a label
for the key, e.g., “exp”, followed by the way that the function will be entered in
the stack so that the argument to the function can be typed at the prompt, e.g.,
“EXP(“. We need not worry about the closing parenthesis, because the
calculator will complete the parentheses before executing the function. The
implementation of function TMENU in ALG mode with the argument list shown
above is as follows. First, we enter the list, then we produce the temporary
menu (see menu key labels) by using function TMENU(ANS(1)). We also
show, in the left-hand side, the result of pressing the
@@exp! soft menu key, i.e., the
prompt EXP(. After typing 8` the result of the operation is shown in the
right-hand side:
A simpler version of the menu can be defined by using
MENU({{”EXP(“,“LN(“,“GAMMA(“,”!(“}).
Enhanced RPN menu
The list presented above for the ALG mode, can be modified slightly to use in
the RPN mode. The modified list will look like this:
{{“exp”,EXP},{“ln”,LN},{“Gamma”,GAMMA},{“!”,!}}