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   1 ;
   2 ; basicEnv.sh
   3 ;
   4 ; Useful things in the BASIC environment
   5 ;
   6 ; © 1994-1998 Straylight
   7 ;
   8
   9 ;----- Licensing note -------------------------------------------------------
  10 ;
  11 ; This file is part of Straylight's BASIC Assembler Supplement.
  12 ;
  13 ; BAS is free software; you can redistribute it and/or modify
  14 ; it under the terms of the GNU General Public License as published by
  15 ; the Free Software Foundation; either version 2, or (at your option)
  16 ; any later version.
  17 ;
  18 ; BAS is distributed in the hope that it will be useful,
  19 ; but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21 ; GNU General Public License for more details.
  22 ;
  23 ; You should have received a copy of the GNU General Public License
  24 ; along with BAS.  If not, write to the Free Software Foundation,
  25 ; 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  26
  27 ; --- Notes ---
  28 ;
  29 ; This file contains symbolic names for the useful bits which BASIC puts
  30 ; after R14 when it CALLs a piece of code.
  31
  32                 ^       0
  33
  34                 ; --- Miscellaneous useful things ---
  35
  36 bEnv_return     #       4                       ;Return address after CALL
  37
  38                 ; --- Offsets from ARGP (in R8 of all places) ---
  39
  40 bEnv_strAcc     #       4                       ;Ptr to string accumulator
  41 bEnv_page       #       4                       ;Current program PAGE
  42 bEnv_top        #       4                       ;Current program TOP
  43 bEnv_loMem      #       4                       ;Current variable start
  44 bEnv_hiMem      #       4                       ;Current stack end
  45 bEnv_memLimit   #       4                       ;Limit of available memory
  46 bEnv_fsa        #       4                       ;Free space start
  47 bEnv_tally      #       4                       ;Value of COUNT
  48 bEnv_timeOff    #       4                       ;Diff tween TIME and OS_Word
  49 bEnv_escWord    #       4                       ;Exception flag word
  50 bEnv_widthLoc   #       4                       ;Value of width-1
  51
  52                 ; --- Internal routines ---
  53                 ;
  54                 ; Some corruptions documented.  Bear in mind that there may
  55                 ; be others, though.
  56
  57 bEnv_varind     #       4                       ;Return value of lvalue
  58                                                 ;Entry: R0 == address of lv
  59                                                 ;       R9 == type of lv
  60                                                 ;       R12 == LINE
  61                                                 ;Exit:  R0-R3 == value
  62                                                 ;       R9 == magic type
  63                                                 ;        0 == str in STRACC
  64                                                 ;        4<<28 == int in R0
  65                                                 ;        8<<28 == fp in R0-R3
  66
  67 bEnv_storea     #       4                       ;Store a value in lvalue
  68                                                 ;Entry: R0-R3 == value
  69                                                 ;       R4 == address of lv
  70                                                 ;       R5 == type of lv
  71                                                 ;       R8 == ARGP
  72                                                 ;       R9 == type of value
  73                                                 ;       R12 == LINE
  74                                                 ;Exit:  R0-R7 corrupted
  75
  76 bEnv_ststore    #       4                       ;Stores a string in variable
  77                                                 ;Entry: Can't remember
  78                                                 ;Exit:  Can't remember
  79
  80 bEnv_lvblnk     #       4                       ;Find a named lvalue
  81                                                 ;Entry: R8 == ARGP
  82                                                 ;       R11 == ptr to name
  83                                                 ;       R12 == LINE
  84                                                 ;Exit:  R0 == address of lv
  85                                                 ;       R9 == type
  86                                                 ;       NE => found var OK
  87                                                 ;       EQ, CS => bad name
  88                                                 ;       EQ, CC => use CREATE
  89
  90 bEnv_create     #       4                       ;Creates a variable
  91                                                 ;Entry: Set up from LVBLNK
  92                                                 ;Exit:  R0 == address of lv
  93                                                 ;       R9 == type
  94
  95 bEnv_expr       #       4                       ;Evaluates an expression
  96                                                 ;Entry: R8 == ARGP
  97                                                 ;       R11 points to string
  98                                                 ;Exit:  As for VARIND
  99                                                 ;       EQ => read string
 100                                                 ;       NE, MI => fp value
 101                                                 ;       NE, PL => int value
 102
 103 bEnv_match      #       4                       ;Tokenises a string
 104                                                 ;Entry: R1 == cr term string
 105                                                 ;       R2 == dest pointer
 106                                                 ;       R3 == 0 (parse lval)
 107                                                 ;             1 (parse rval)
 108                                                 ;       R4 == 0/&8D (line no)
 109                                                 ;Exit:  R0, R3, R4 corrupted
 110                                                 ;       R1 == ptr past cr
 111                                                 ;       R2 == ptr past cr
 112                                                 ;       R5 == status:
 113                                                 ;        >=&1000 mis-()
 114                                                 ;        bit 8 => bad line no
 115                                                 ;        lsb==1 => mis-""
 116
 117 bEnv_tokenAddr  #       4                       ;Untokenises a string
 118                                                 ;Entry: R0 == token
 119                                                 ;       R12 == ptr to next ch
 120                                                 ;Exit:  R1 == ptr to string
 121                                                 ;             (term >&7f)
 122                                                 ;       R12 modified
 123                                                 ;       R0 corrupted
 124
 125                 ; --- Floating point routines ---
 126                 ;
 127                 ; * means R4-R7 corrupted, and errors (e.g. overflow)
 128                 ; possible.
 129                 ;
 130                 ; In all cases, (R0-R3) may be modified, although the FP
 131                 ; value will be preserved (e.g. for normalisation).
 132                 ;
 133                 ; In FIX and FLOAT, R9 is changed to indicate the new type.
 134
 135                 #       8                       ;Ask Roger/Sophie!
 136 bEnv_fSta       #       4                       ;[R9] <- (R0-R3)
 137 bEnv_fLda       #       4                       ;(R0-R3) <- [R9]
 138
 139 bEnv_fAdd       #       4                       ;(R0-R3) <- [R9] + (R0-R3)  *
 140 bEnv_fSub       #       4                       ;(R0-R3) <- [R9] - (R0-R3)  *
 141 bEnv_fMul       #       4                       ;(R0-R3) <- [R9] * (R0-R3)  *
 142 bEnv_fDiv       #       4                       ;(R0-R3) <- [R9] / (R0-R3)  *
 143
 144 bEnv_float      #       4                       ;(R0-R3) <- R0, R9 <- FLOAT
 145 bEnv_fix        #       4                       ;R0 <- (R0-R3), R9 <- INT
 146 bEnv_fSqrt      #       4                       ;(R0-R3) <- sqrt(R0-R3)     *
 147
 148 ;----- That's all, folks ----------------------------------------------------
 149
 150                 END