Four types of RPN

[Thomas Klemm]

(09-10-2014 02:04 AM)htom trites Wrote:  It is more useful on a drop to stuff a 1 into t (assuming a constant size stack), rather than a 0 (1 being more used than 0 in computations), although echoing t is also useful.

In case of a constant stack size this is what probably happens behind the scene:

Code:

L = X
X = Y ∘ X
Y = Z
Z = T

Thus T isn't changed at all.

Cheers
Thomas

[Marcus von Cube]

The HP 35 has limited memory and uses its T register for intermediate calculations in some transcendental functions. It makes sense to clear T after its "abuse" in order to avoid presenting garbage to the user. So as long as you don't use any transcendental functions, the behavior is "top copy", but top can be cleared on occasion.

Edit: I just read in another thread that only the trig functions are affected and that the HP 35 duplicates Z to T after such an operation.

[walter b]

Well, well, the claim was top copy versus

Quote:top is zeroed (HP-35 does this until T has a non-zero value)

Learning English together again ... (or: How shall I know what I meant until I read what I wrote?).

d:-/

[Thomas Klemm]

(09-11-2014 10:19 AM)Marcus von Cube Wrote:  The HP 35 has limited memory and uses its T register for intermediate calculations in some transcendental functions. It makes sense to clear T after its "abuse" in order to avoid presenting garbage to the user. So as long as you don't use any transcendental functions, the behavior is "top copy", but top can be cleared on occasion.

There's an instruction stack -> a that drops the X register from the stack and moves it to register a:

X → a
Y → X
Z → Y
T → Z

There's another instruction c -> stack that pushes register c to the stack. After executing this instruction the previous value of the T register is lost.

Z → T
Y → Z
X → Y
c → X

Thus the intermediate result during the calculations of transcendental functions is saved in the X register and not in the T register.

Quote:Edit: I just read in another thread that only the trig functions are affected and that the HP 35 duplicates Z to T after such an operation.

With the instruction stack -> a the T register is duplicated to the Z register.

Cheers
Thomas

[axd1967]

(09-11-2014 10:19 AM)Marcus von Cube Wrote:  The HP 35 has limited memory and uses its T register for intermediate calculations in some transcendental functions. It makes sense to clear T after its "abuse" in order to avoid presenting garbage to the user. So as long as you don't use any transcendental functions, the behavior is "top copy", but top can be cleared on occasion.

Edit: I just read in another thread that only the trig functions are affected and that the HP 35 duplicates Z to T after such an operation.

BTW - sounds like a waste of time/energy to clear the register: does a zero help the user more than a random value?

[axd1967]

(09-11-2014 10:19 AM)Marcus von Cube Wrote:  Edit: I just read in another thread that only the trig functions are affected and that the HP 35 duplicates Z to T after such an operation.

That other thread would be this one ? :-)

[Marcus von Cube]

(09-11-2014 05:11 PM)axd1967 Wrote:  That other thread would be this one ? :-)

Of course...