Maths (Geometry): arctanTable

       Name: arctanTable                                             [Show more]
       Type: Variable
   Category: Maths (Geometry)
    Summary: Arctan lookup table
  Deep dive: Flying by mouse
    Context: See this variable in context in the source code
 References: This variable is used as follows:
             * arctanTableAddr uses arctanTable


 At byte n, the table contains:

   ((2^31 - 1) / PI) * arctan(n / 128)

 For n = 0 to 127

 In the original BBC BASIC source, this table would have been populated using
 something along these lines:

   FOR I% = 0 TO 127
    [
     OPT pass%
     EQUD ((2^31 - 1) / PI) * ATN(I% / 128)
    ]
   NEXT

 I have used EQUDs here because different computers have different algorithms
 and accuracies in their maths routines, so the only way to ensure a complete
 match with the original binaries is to hard-code the values.

 The above loop produces the correct values when run on an Archimedes.


.arctanTable

 EQUD     &00000000, &00517C55, &00A2F61E, &00F46AD0
 EQUD     &0145D7E1, &01973AC7, &01E890FC, &0239D7FB
 EQUD     &028B0D43, &02DC2E53, &032D38B3, &037E29EB
 EQUD     &03CEFF89, &041FB721, &04704E4A, &04C0C2A4
 EQUD     &051111D4, &05613983, &05B13767, &06010937
 EQUD     &0650ACB6, &06A01FAE, &06EF5FF1, &073E6B5A
 EQUD     &078D3FCE, &07DBDB3A, &082A3B94, &08785EDF
 EQUD     &08C64325, &0913E67C, &09614703, &09AE62E6
 EQUD     &09FB385B, &0A47C5A2, &0A940907, &0AE000E1
 EQUD     &0B2BAB95, &0B77078F, &0BC2134B, &0C0CCD4E
 EQUD     &0C57342A, &0CA1467C, &0CEB02EF, &0D346836
 EQUD     &0D7D7514, &0DC62856, &0E0E80D4, &0E567D73
 EQUD     &0E9E1D23, &0EE55EE2, &0F2C41B6, &0F72C4B3
 EQUD     &0FB8E6F9, &0FFEA7B0, &1044060F, &10890156
 EQUD     &10CD98D1, &1111CBD6, &115599C6, &1199020E
 EQUD     &11DC0423, &121E9F86, &1260D3C1, &12A2A069
 EQUD     &12E4051D, &13250183, &1365954E, &13A5C038
 EQUD     &13E58203, &1424DA7D, &1463C97A, &14A24ED7
 EQUD     &14E06A7A, &151E1C50, &155B6450, &15984275
 EQUD     &15D4B6C4, &1610C149, &164C6216, &16879945
 EQUD     &16C266F6, &16FCCB50, &1736C67E, &177058B5
 EQUD     &17A9822C, &17E24322, &181A9BDA, &18528C9E
 EQUD     &188A15BB, &18C13785, &18F7F252, &192E467F
 EQUD     &1964346D, &1999BC80, &19CEDF21, &1A039CBD
 EQUD     &1A37F5C4, &1A6BEAA9, &1A9F7BE4, &1AD2A9EF
 EQUD     &1B057548, &1B37DE6E, &1B69E5E5, &1B9B8C33
 EQUD     &1BCCD1DF, &1BFDB775, &1C2E3D81, &1C5E6491
 EQUD     &1C8E2D38, &1CBD9807, &1CECA593, &1D1B5671
 EQUD     &1D49AB3A, &1D77A486, &1DA542F0, &1DD28713
 EQUD     &1DFF718C, &1E2C02F7, &1E583BF4, &1E841D21
 EQUD     &1EAFA71E, &1EDADA8D, &1F05B80D, &1F304042
 EQUD     &1F5A73CC, &1F84534E, &1FADDF6B, &1FD718C5