b3300876@rick.cs.ubc.ca (george kai yee chow) (09/25/90)
I have two questions. The first is really minor but I'm sure most people would want an answer: How do I speed up Tetris for the 48sx. Right now, the game is so slow that I can take notes and play a game very comfortably. Not that I don't like this but I really would like a more challenging game. The second is wrt the cosine function. I was doing some geometry problem and needed to evaluate cos(pi/3) (I know, I know, I should know it but I thought I might as well fire up my 48 just for fun). My 48sx returned 0.4999..., not 0.5. sin(pi/6) does return 0.5 though. Why is this? George Chow
bson@rice-chex.ai.mit.edu (Jan Brittenson) (09/25/90)
In article <1990Sep24.183934.575@rick.cs.ubc.ca> b3300876@rick.cs.ubc.ca (george kai yee chow) writes: > I was doing some geometry problem and needed to evaluate cos(pi/3) (I > know, I know, I should know it but I thought I might as well fire up > my 48 just for fun). My 48sx returned 0.4999..., not 0.5. sin(pi/6) > does return 0.5 though. Why is this? If you do pi 3 / ->NUM pi 6 / ->NUM / you get "2.00000000001", i.e. a rounding error. My guess is that there is more of a rounding error when dividing pi with the prime 3 than when dividing with the even number 6. Now, I personally would like 'cos(pi/3)' ->EVAL (as opposed to ->NUM) to pass the algebraic 'pi/3' to cos, and cos to recognize this as a know special form. (But only when the numerical-results flag is clear.) It would be nice if typing pi 3 / cos resulted in the same - the precise answer 0.5. (There are plenty of good algorithms yielding the precise answer of fractions of pi.) Hmm... this could be done with ^MATCH... Write a function cospi so that 'cospi(3)' is the precise answer of 'cos(pi/3)' and do { 'cos(pi/&piD)' 'cospi(&piD)' } ^MATCH Does anyone know how to use the third list entry, the 'conditional'? It seems you can't refer to the variables in the patterns, for instance.
SLSW2@cc.usu.edu (Roger Ivie) (09/25/90)
In article <1990Sep24.183934.575@rick.cs.ubc.ca>, b3300876@rick.cs.ubc.ca (george kai yee chow) writes: > > The second is wrt the cosine function. I was doing some > geometry problem and needed to evaluate cos(pi/3) (I know, I > know, I should know it but I thought I might as well fire up > my 48 just for fun). My 48sx returned 0.4999..., not 0.5. > sin(pi/6) does return 0.5 though. Why is this? > One of the more interesting things I encountered when I bought my first HP calculator (a 31E) was a long discussion in the manual about this sort of problem (I've still got the manual, but it's not handy. If anyone's interested, I can find a direct quote). The gist of the discussion was that since the calculator could not really use pi but only a 10-digit approximation of pi, the result of the calculator is accurate. It is returning the cosine of precisely that 10-digit approximation of (pi/3). -- =============================================================================== Roger Ivie 35 S 300 W Logan, Ut. 84321 (801) 752-8633 ===============================================================================
b3300876@rick.cs.ubc.ca (george kai yee chow) (09/26/90)
In article <36159@cc.usu.edu> SLSW2@cc.usu.edu (Roger Ivie) writes: >In article <1990Sep24.183934.575@rick.cs.ubc.ca>, b3300876@rick.cs.ubc.ca (george kai yee chow) writes: >> >> The second is wrt the cosine function. I was doing some >> geometry problem and needed to evaluate cos(pi/3) (I know, I >> know, I should know it but I thought I might as well fire up >> my 48 just for fun). My 48sx returned 0.4999..., not 0.5. >> sin(pi/6) does return 0.5 though. Why is this? >> >One of the more interesting things I encountered when I bought my first >HP calculator (a 31E) was a long discussion in the manual about this sort >of problem (I've still got the manual, but it's not handy. If anyone's >interested, I can find a direct quote). > >The gist of the discussion was that since the calculator could not really >use pi but only a 10-digit approximation of pi, the result of the calculator >is accurate. It is returning the cosine of precisely that 10-digit >approximation of (pi/3). Yes, I'm aware of the problem of calculating with pi. But as I recall reading in the 48sx's manual, the symbol modes was suppose to elminate that. On the 48sx, you can ask to keep pi as a symbol to avoid the rounding error. >=============================================================================== >Roger Ivie > >35 S 300 W >Logan, Ut. 84321 >(801) 752-8633 >=============================================================================== George
edp@jareth.enet.dec.com (Eric Postpischil (Always mount a scratch monkey.)) (09/27/90)
In article <1990Sep26.160424.12956@rick.cs.ubc.ca>, b3300876@rick.cs.ubc.ca (george kai yee chow) writes: >Yes, I'm aware of the problem of calculating with pi. But as I recall reading >in the 48sx's manual, the symbol modes was suppose to elminate that. On the >48sx, you can ask to keep pi as a symbol to avoid the rounding error. There's a limit to how far the calculator can go with symbolic manipulation. The calculator will preserve 'pi' as a symbolic in expressions. When taking sines or cosines, it will recognize pi and pi/2 and return exact results. In other cases, it does not have exact results prepared for fractions of pi. So, to complete the calculation and return a number, it must convert the symbolic 'pi' to a number and perform numeric calculations. -- edp
b3300876@rick.cs.ubc.ca (george kai yee chow) (09/28/90)
In article <15643@shlump.nac.dec.com> edp@jareth.enet.dec.com (Eric Postpischil (Always mount a scratch monkey.)) writes: >In article <1990Sep26.160424.12956@rick.cs.ubc.ca>, b3300876@rick.cs.ubc.ca >(george kai yee chow) writes: > >>Yes, I'm aware of the problem of calculating with pi. But as I recall reading >>in the 48sx's manual, the symbol modes was suppose to elminate that. On the >>48sx, you can ask to keep pi as a symbol to avoid the rounding error. > >There's a limit to how far the calculator can go with symbolic manipulation. >The calculator will preserve 'pi' as a symbolic in expressions. When taking >sines or cosines, it will recognize pi and pi/2 and return exact results. In >other cases, it does not have exact results prepared for fractions of pi. So, >to complete the calculation and return a number, it must convert the symbolic >'pi' to a number and perform numeric calculations. Another reason why I mentioned it is because both of my Casio's (fx-451M and fx-8000G) return cos(pi/6) correctly and clearly they only use an approximation of pi. > > > -- edp George
lishka@uwslh.slh.wisc.edu (a.k.a. Chri) (09/28/90)
b3300876@rick.cs.ubc.ca (george kai yee chow) writes: >I have two questions. The first is really minor but I'm sure >most people would want an answer: How do I speed up Tetris >for the 48sx. Right now, the game is so slow that I can >take notes and play a game very comfortably. Not that I don't >like this but I really would like a more challenging game. I would think that the way to speed it up is to write it in the CHIP48 language. This would bypass the slowness associated with interpreted RPL and garbage collection, because CHIP48 is written in machine code and its language is much easier to interpret. With a little ingenuity and planning, I don't think tetris would be too hard to accomplish with CHIP48. .oO Chris Oo. -- Christopher Lishka 608-262-4485 "Dad, don't give in to mob mentality!" Wisconsin State Lab. of Hygiene -- Bart Simpson lishka@uwslh.slh.wisc.edu "I'm not, Son. I'm jumping on the bandwagon." uunet!uwvax!uwslh!lishka -- Homer Simpson
b3300876@rick.cs.ubc.ca (george kai yee chow) (09/30/90)
In article <1990Sep28.141706.24027@uwslh.slh.wisc.edu> lishka@uwslh.slh.wisc.edu (a.k.a. Chri) writes: >I would think that the way to speed it up is to write it in the CHIP48 >language. This would bypass the slowness associated with interpreted >RPL and garbage collection, because CHIP48 is written in machine code >and its language is much easier to interpret. With a little ingenuity >and planning, I don't think tetris would be too hard to accomplish >with CHIP48. Could anyone explain to me what CHIP48 is? I was off of c.s.h from the last week of August and I seem to have missed everything wrt CHIP48. Is is an alternative language for the HP? Is it still an interpreter? Where is it documented? Ie, how do I go about learning it? > .oO Chris Oo. >-- >Christopher Lishka 608-262-4485 "Dad, don't give in to mob mentality!" >Wisconsin State Lab. of Hygiene -- Bart Simpson > lishka@uwslh.slh.wisc.edu "I'm not, Son. I'm jumping on the bandwagon." > uunet!uwvax!uwslh!lishka -- Homer Simpson George Chow