Changes between Version 24 and Version 25 of NumericTower


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Timestamp:
10/17/13 12:59:58 (4 years ago)
Author:
cowan
Comment:

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  • NumericTower

    v24 v25  
    33This is an analysis of the R5RS provision that the full numeric tower may be subsetted.  Four boolean feature settings characterize different kinds of numeric towers: `exactness-preserving`, `ratios`, `inexact`, and `complex`.  These refer respectively to the closure of exact numbers under rational operations (except `/`), exact non-integer values, inexact rationals, and non-real numbers. 
    44 
    5 There are therefore 16 possible numeric towers.  Nine of them are known to have implementations, as shown below.  I write `+` if a feature is present and `-` if it is absent, and give a general description of the resulting tower and some Scheme implementations that provide it. 
     5There are therefore 16 possible numeric towers.  8 of them are known to have implementations, as shown below.  I write `+` if a feature is present and `-` if it is absent, and give a general description of the resulting tower and some Scheme implementations that provide it. 
    66 
    77||`exactness-preserving`||`ratios`||`inexact`||`complex`||Description||Implementations 
    88||-||-||-||-||A "toy" tower with bounded exact integers only (possibly appropriate where no numerical work will be done)||!SigScheme*|| 
    9 ||-||-||+||-||Fixnums and flonums (all arithmetic runs in essentially constant time)||Plain Chicken, Shoe*, !TinyScheme*, RScheme, BDC*, XLisp*, Schemik*, VX, SXM*, Inlab, Sixx, Sizzle (also Elisp*, C*)|| 
    10 ||-||-||+||+||Fixnums, flonums, and inexact complex numbers (all arithmetic runs in essentially constant time)||Stalin|| 
     9||-||-||+||-||Fixnums and flonums (all arithmetic runs in essentially constant time)||Plain Chicken, Shoe*, !TinyScheme*, RScheme, BDC*, XLisp*, Schemik*, VX, SXM*, Inlab, Sixx, Sizzle, Stalin (also Elisp*, C*)|| 
    1110||-||+||+||+||Limited-range exact and inexact numbers||S7, Wraith|| 
    1211||+||-||+||-||Exact integers and inexact real numbers (a good all-round compromise)||Bigloo, Scheme 9, Elk (also ISLisp)||