Hi all, I've been playing with the number tower in Racket and I noticed it appears to drift from the R5RS and R6RS standard. Now, I know the Racket rebrand grants PLT
Scheme to now drift from the standard, but I think this may actually be unintentional. So let me know if I've misunderstood this. Section 7.1.1 or R5RS [1] states: """ <number> -> <num2> | <num8> | <num10> | <num16> The following rules for <num R>, <complex R>, <real R>, <ureal R>, <uinteger R>, and <prefix R> should be replicated for R = 2, 8, 10, and 16. There are no rules for <decimal 2>, <decimal 8>, and <decimal 16>, which means that numbers containing decimal points or exponents must be in decimal radix. """ Section 4.2 of R6RS [2] states: """ The rules for <num R>, <complex R>, <real R>, <ureal R>, <uinteger R>, and <prefix R> below should be replicated for R = 2, 8, 10, and 16. There are no rules for <decimal 2>, <decimal 8>, and <decimal 16>, which means that number representations containing decimal points or exponents must be in decimal radix. """ However, Racket accepts number representations with decimals or exponents [3]. Trying this out on other implementations of varying conformance, I see that SISC [4], Bigloo [5] and Guile [6] don't allow this. Am I misunderstanding the specification here or is this a bug or is Racket intentionally doing something outside the standard? Thanks for the help! Ewan [1] http://www.schemers.org/Documents/Standards/R5RS/HTML/r5rs-Z-H-10.html#%_sec_7.1.1 [2] http://www.r6rs.org/final/html/r6rs/r6rs-Z-H-7.html#node_sec_4.2 [3] Here's what I put into Racket: Welcome to Racket v5.0. > 1.0 1.0 > 1e10 10000000000.0 > #o6 6 > #o60 48 > #o60.3 ;<=== 48.375 > #b10 2 > #b10.10 ;<=== 2.5 > #b10e10 ;<=== 8.0 This doesn't seem correct. #o and #b shouldn't accept decimals or exponents. It should either return two values as entering "> 1 1" would or it should yield an error. [4] Here's what I put into SISC 1.16.6: #;> 1 1 #;> 1e10 1.0e10 #;> #o6 6 #;> #o60 48 #;> #o60.3 Error in read-code: error reading from port '#<character-input-port>': unexpected token where number was mandatory. --------------------------- To enable more detailed stack tracing, set the dynamic parameter max-stack-trace-depth to a non-zero value, e.g. 16. --------------------------- Some stack trace entries may have been suppressed. To see all entries set the dynamic parameter suppressed-stack-trace-source-kinds to '(). #;> #b10 2 #;> #b10.10 Error in read-code: error reading from port '#<character-input-port>': unexpected token where number was mandatory. #;> #b10e10 Error in read-code: error reading from port '#<character-input-port>': unexpected token where number was mandatory. [5] Here's what I put into Bigloo (3.4a) 1:=> 1 1 1:=> 1e10 1.0e10 1:=> #o6 6 1:=> #o60 48 1:=> #o60.3 48 1:=> 0.3 1:=> #b10 2 1:=> #b10.10 2 1:=> 0.1 1:=> #b10e10 2 1:=> *** ERROR:eval: Unbound variable (from top-level) -- e10 What bigloo does is more surprising at first since it's parsing the octal #o60.3 as two numbers, #o60 and 0.3. And it's correct to yield an error with #b10e10. But I think this is inline with the standard. [6] Here's what Guile 1.8.7 says: guile> 1 1 guile> 1e10 1.0e10 guile> #o6 6 guile> #o60 48 guile> #o60.3 ERROR: In procedure scm_lreadr: ERROR: #<unknown port>:5:1: unknown # object ABORT: (read-error) guile> #b10 2 guile> #b10.10 ERROR: In procedure scm_lreadr: ERROR: #<unknown port>:7:1: unknown # object ABORT: (read-error) guile> #b10e10 ERROR: In procedure scm_lreadr: ERROR: #<unknown port>:8:1: unknown # object ABORT: (read-error) _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
