Deviations from the standard (historical revision 2540)

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Deviations from the standard

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[4.1.3] The maximal number of arguments that may be passed to a compiled procedure or macro is 120. A macro-definition that has a single rest-parameter can have any number of arguments. If the libffi library is available on this platform, and if it is installed, then CHICKEN can take advantage of this. See the README file for more details.
[4.2.2] letrec does evaluate the initial values for the bound variables sequentially and not in parallel, that is:

 (letrec ((x 1) (y 2)) (cons x y))

is equivalent to

 (let ((x (void)) (y (void)))
   (set! x 1)
   (set! y 2)
   (cons x y) )

where R5RS requires

 (let ((x (void)) (y (void)))
   (let ((tmp1 1) (tmp2 2))
     (set! x tmp1)
     (set! y tmp2)
     (cons x y) ) )

[4.3] syntax-rules macros are not provided but available separately.
[6.2.4] The runtime system uses the numerical string-conversion routines of the underlying C library and so does only understand standard (C-library) syntax for floating-point constants.
[6.2.5] There is no built-in support for rationals, complex numbers or extended-precision integers (bignums). The routines complex?, real? and rational? are identical to the standard procedure number?. The procedures numerator, denominator, rationalize, make-rectangular and make-polar are not implemented. Support for extended numbers is available as a separate package, provided the GNU multiprecision library is installed.
[6.2.6] The procedure string->number does not obey read/write invariance on inexact numbers.
[6.4] The maximum number of values that can be passed to continuations captured using call-with-current-continuation is 120.
[6.5] Code evaluated in scheme-report-environment or null-environment still sees non-standard syntax.
[6.6.2] The procedure char-ready? always returns #t for terminal ports. The procedure read does not obey read/write invariance on inexact numbers.
[6.6.3] The procedures write and display do not obey read/write invariance to inexact numbers.
[6.6.4] The transcript-on and transcript-off procedures are not implemented.