I mean no disrespext but I'm not sure that this message is correct in the details. What is the point being made here?
Robby On Wednesday, October 13, 2010, synx <p...@synx.us.to> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 10/13/2010 05:36 PM, Mathew Kurian wrote: > >> Racket as a language built on top of another base language (i.e. >> Assembly or C) > > No, racket is not built on top of another base language. > >> or is it directly connected to the processor language? > > The language racket does not directly translate to the processor > 'language'. The racket program reads that language in, and based on what > it reads, sends a sequence of instructions to one, or more processors. > These sequences are optimized "in time" so that they will only always > work at the time they are executed, so you couldn't save them to a file > and replay them 10 minutes later, hoping the computer would do the same > thing. > > The following example for instance: > > (module example racket/base > > (let sum ((i (random 5))) > (if (<= i 0) 0 > (+ i (sum (- i 1)))))) > > The assembly language directives racket might produce when evaluating > that program could be as follows: first it produces the assembly needed > to get a random number between 0 and 5. Then it produces the assembly to > add 1 and 0 (the innermost recursion), then 2 and 1, then 3 and 2, then > 5 and 4. Then it produces the assembly to print out the number 9. The > racket program can and will analyze such loops, and unroll them so that > the assembler never sees a single jump instruction, even if the amount > of times the loop is executed is only determined the moment of the > code's evaluation. Or maybe it won't. But the point is that if you saved > the instructions it produced, that is > > < random number 0 to 5 ... > > < add 1 and 0 > > < add 2 and 1 > > < add 3 and 2 > > < add 4 and 5 > > < display 9 to stdout > > > And then you blindly executed those instructions again, it would > calculate that random number, then ignore it, add up 0 to 4, then ignore > that result, then display 9 to standard output every time. But if you > ran racket on that program again, it would produce varying amounts of > "add" instructions, and in fact sometimes it would provide a single add > instruction followed by a jump-if-zero loop, if the amount of iterations > is deemed too high by the optimizing compiler to unroll. > > You can convert racket to a byte code format (using raco make) but > that's as far as you can go before the resulting programs may change > unpredictably between two executions of the same code. Any further and > you will most certainly lose vital state information, like trying to > optimize the construction of your roller coaster by removing the track. > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v2.0.14 (GNU/Linux) > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ > > iQEcBAEBAgAGBQJMtmW2AAoJECC/cKf8E7UIz+gH/j3i9s2y0/8pYb9wOuPO6xkW > wozUwEKTg9vcV7jf9AR7obepReTsJalljahd7q2yfsldH4KwpvklWr7mAvEHw56Z > 35g23gbTW3MVmSmkEinJ0PhV11JUyD3bUIrQUTNmk4XNR88+7A0k2ye7osDB7Uef > PViJyrr1JG2DrMaCpNGvWOE735keda12Hr7B5YeEI6+ECd/inHOkC2HP34OpL+Qd > Skth1MWAvR+khZAAwhEdKyu/cL9ebEI4y/aReJ98Z/7EnP84RcDT0GCbPLnGtahC > JTw3VoHggJ1wmLP9IIutKW3s5c944Yr6jrA1HrEPOHVaBSGHlG2YE32pN8qlrJ0= > =bF85 > -----END PGP SIGNATURE----- > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/users > _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
