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Split some code into separate files for easier management (3) Because the source for lwbasic is so large, split it into several different files to make it easier to navigate and modify. This is part three of the split. Includes a file missing from part one.
author William Astle <lost@l-w.ca>
date Sun, 06 Aug 2023 00:41:26 -0600
parents e74d00ac6b79
children eb2681108660
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1 *pragmapush list
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2 *pragma list
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3 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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4 ; Fetch next input character, skip spaces. This is structured the way it is to avoid burning any register except A
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5 ; which is used for the returned value. Z will be set if the input character is NUL or a colon. C will be set if the
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6 ; input character is an ASCII digit. This allows testing Z to identify the end of a command due to either a colon or
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7 ; the end of a line.
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8 ;
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9 ; Compared to Color Basic, the instruction sequence only varies in the handling of the LDA. In Color Basic, the sequence
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10 ; is an LDA extended followed by a JMP extended. This totals to 9 cycles (5 for LDA, 4 for JMP). In LWBasic, an LDA
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11 ; with extended indirect addressing is used. This also totals 9 cycles. The only other difference is when a space is
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12 ; detected where the branch can be direct to the nextchar code instead of having to branch around a direct page JUMP
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13 ; which saves 3 cycles for the case where a space is detected. In other words, this is only slower by virtue of the
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14 ; fact that it is called with an extended JSR instead of a direct JSR which causes one extra cycle to be used there
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15 ; and one extra byte for each call to nextchar or curchar.
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16 ;
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17 ; On 6309, native move saves an extra cycle in the LDA sequence using the LDA extended followed by JMP extended
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18 ; sequence.
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19 ;
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20 ; This whole thing could be sped up by keeping the input pointer in a register. However, retaining the ability to
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21 ; use Y without having to save it first is likely more beneficial.
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22 nextchar inc inputptr+1 ; bump LSB of input pointer
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23 bne curchar ; brif no carry
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24 inc inputptr ; bump MSB
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25 curchar lda [inputptr] ; read the byte
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26 cmpa #'9+1 ; clear C if above ASCII digits, Z if colon
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27 bhs curchar0 ; brif above the ASCII digits
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28 cmpa #0x20 ; is it a space?
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29 beq nextchar ; brif so - skip over it
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30 suba #'0 ; clever way to set C if >= ASCII 0, Z if zero
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31 suba #-'0
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32 curchar0 rts
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33 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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34 ; This is exactly the same as nextchar except it doesn't skip spaces. Unfortunately, for efficiency purposes, we need
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35 ; to actually duplicate code here.
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36 nextcharraw inc inputptr+1 ; bump LSB of input pointer
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37 bne curchar ; brif no carry
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38 inc inputptr ; bump MSB
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39 curcharraw lda [inputptr] ; fetch the byte
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40 cmpa #'9+1 ; clear C if above digits, set Z if colon
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41 bhs curcharraw0 ; brif above digits
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42 suba #'0 ; clever way to set C if >= ASCII 0, Z if zero
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43 suba #-'0
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44 curcharraw0 rts
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45 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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46 ; Immediate mode handler
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47 immediate jsr writecondnl ; do newline if required
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48 ldx #prompt ; point to prompt string
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49 jsr console_outstrn
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50 immediate0 jsr readline ; read input line
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51 bcs immediate0 ; brif ended with BREAK
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52 ldx #linebuff ; point to start of line input buffer
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53 stx inputptr ; set input pointer
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54 jsr curchar ; skip spaces and set flags
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55 bcs immediate1 ; brif there's a line number
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56 tsta ; is there anything there at all (end of line)?
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57 beq immediate0 ; brif not - read another line
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58 ldx inputptr ; get the modified input pointer processing above
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59 jsr tokenize ; tokenize the line at inputptr, return with result at tokebuff and X
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60 jsr interpretline ; go interpret the tokenized line
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61 bra immediate ; go handle another line
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62 immediate1 bsr parse_lineno ; parse the line number
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63 bsr prog_findline ; go see if the line is in the program
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64 bne immediate3 ; brif not - no need to delete it
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65 ldu ,x ; get next line pointer which is where we start the copy from
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66 leay ,x ; use temp pointer for copying
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67 immediate2 lda ,u+ ; get source byte
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68 sta ,y+ ; stash it
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69 cmpu vartab ; did we reach the end of the program text?
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70 blo immediate2 ; brif not
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71 sty vartab ; save new end of program
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72 immediate3 jsr curchar ; skip any spaces after line number
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73 tsta ; is it the end of input (don't test for colon)
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74 beq immediate6 ; brif so - we don't need to insert a line
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75 pshs x ; save program insert location and line number
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76 ldx inputptr ; point to line text
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77 jsr tokenize ; tokenize line, get length to D
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78 leay ,x ; save tokenized line pointer
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79 addd #4 ; account for next line pointer and line number
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80 ldx vartab ; get start of copy location
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81 leau d,x ; set destination copy location D bytes further up
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82 stu vartab ; save new end of program
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83 immediate4 lda ,-x ; get byte from program
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84 sta ,-u ; stash it above the empty space
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85 cmpx ,s ; did we reach the insertion point?
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86 bne immediate4 ; brif not - keep going
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87 leas 2,s ; clear insertion location
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88 stu ,x++ ; set next line pointer to not null
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89 ldd binval ; set the line number for the program
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90 std ,x++
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91 immediate5 lda ,y+ ; get byte from tokenized line
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92 sta ,x+ ; stash it in the program
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93 bne immediate5 ; brif not at end of tokenized line (see note for fixlineptrs)
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94 immediate6 bsr prog_fixlineptrs ; fix up line pointers (all of them)
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95 ldx vartab ; clear out variables
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96 stx objecttab
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97 stx freestart
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98 bra immediate0 ; go handle more input
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99 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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100 ; Fix up next line pointers. Enter at prog_fixlineptrs to do the entire program. Enter at prog_fixlineptrsx to start
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101 ; at the line pointered to by X, which MUST NOT point to the end of the program.
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102 ;
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103 ; Works by simply scanning for a NUL in the program text after a line header (pointer to next line and line number)
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104 ; and uses that as the new next line pointer. A NULL next line pointer flags the end of the program.
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105 ;
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106 ; Observation: if the program text format is changed such that it can include NULs embedded within a line, this routine
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107 ; will need to be updated to grok that.
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108 prog_fixlineptrs
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109 ldx progtext ; point to start of program
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110 prog_fixlineptrsx
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111 ldu ,x ; are we at the end of the program?
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112 beq prog_findline2 ; brif not (borrow RTS from findline)
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113 leau 4,x ; point to line text (past pointer and line number)
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114 prog_fixlineptrs1
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115 lda ,u+ ; are we at the end of this line?
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116 bne prog_fixlineptrs1 ; brif not
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117 stu ,x ; set the next pointer for the previous line
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118 leax ,u ; move to the next line
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119 bra prog_fixlineptrsx ; go handle the next line
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120 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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121 ; Find a line in the program. Returns with C set and Z clear if no match and C clear and Z set if a match is found. X
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122 ; will point to either the exact matched line *or* the line that would be immediately after the desired line number if
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123 ; the line had been present, which could be the end of the program. D and U are clobbered. Enter at prog_findlinex to
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124 ; start searching at the line pointed to by X. Enter at prog_findline to start at the beginning of the program. Enter
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125 ; with the desired line number in binval.
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126 prog_findlinecl ldx curline ; get current line pointer
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127 beq prog_findline ; brif immediate mode
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128 ldd binval ; get desired line number
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129 cmpd 2,x ; is the desired line number >= current line?
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130 beq prog_findline2 ; brif this is the right line (optimizes goto self)
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131 bhi prog_findlinex ; brif desired line higher: start here instead of program start
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132 prog_findline ldx progtext ; point to start of program
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133 prog_findlinex ldu binval ; get line number to search for
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134 prog_findline0 ldd ,x ; end of program?
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135 beq prog_findline1 ; brif not
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136 cmpu 2,x ; does line number match? Z set if so, clear if not; C set not found
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137 bls prog_findline2
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138 ldx ,x ; move to next line
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139 bra prog_findline0 ; see if we found the line yet
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140 prog_findline1 coma ; set carry for not found; also clears Z because D is zero from above
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141 prog_findline2 rts
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142 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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143 ; Parse a line number and return it in binval; raise syntax error if the line number overflows 16 bits unsigned.
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144 ; Preserves; registers except D. This will accept the entire 16 bit unsigned number range which is why there is
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145 ; a BCS after every shift or add. Enter with the input pointer pointing to the number to parse.
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146 parse_lineno ldd zero ; clear out accumlator but preserve carry flag
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147 std binval
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148 jsr curchar ; set flags on current character; skip spaces
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149 bcc parse_lineno1 ; brif first character wasn't a digit - default to zero
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150 parse_lineno0 suba #0x30 ; adjust to binary digit
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151 pshs a ; save digit so we can add it later
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152 ldd binval ; get accumulated number
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153 lslb ; multiply accumulator by 10
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154 rola ; times 2
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155 bcs SNERROR ; brif overflow
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156 lslb
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157 rola ; times 4
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158 bcs SNERROR ; brif overflow
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159 addd binval ; times 5 (add orignal value to times 4)
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160 bcs SNERROR ; brif overflow
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161 lslb
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162 rola ; times 10
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163 bcs SNERROR ; brif overflow
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164 addb ,s+ ; add in accumulated digit
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165 adca #0
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166 bcs SNERROR ; brif overflow
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167 std binval ; save accumulated number
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168 jsr nextcharraw ; get next input character; DO NOT skip spaces
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169 bcs parse_lineno0 ; brif it's also a digit
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170 parse_lineno1 rts
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171 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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172 ; Main interpretation loop
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173 ;
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174 ; Enter at interpret with inputptr pointing to the code stream to interpret.
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175 ; Enter at interpretline with X pointing to the command stream to interpret which will return to the caller one the
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176 ; command stream has completed. STOP or BREAK will return with carry set while END or falling off the end of the
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177 ; code will return with carry clear. In the event of an error, the usual error processing will be done and control
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178 ; will return to immediate mode with the stack reset.
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179 interpret jsr breakcheck ; check for BREAK
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180 bcs cmd_stop0 ; brif BREAK detected - go stop the program
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181 ldx inputptr ; get interpration address
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182 stx curstmt ; save address of the current statement (needed for some stuff)
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183 lda ,x+ ; are we at the end of the line?
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184 beq interpret0 ; brif so
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185 cmpa #': ; end of statement?
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186 beq interpret3 ; brif so - do a statement
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187 SNERROR ldb #err_sn ; raise a syntax error
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188 jmp ERROR
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189 interpret0 sta endflag ; flag the program exit state as "END" (will be zero)
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190 ldd curline ; were we in immediate mode?
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191 bne interpret1 ; brif not
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192 clra ; clear carry to indicate normal exit
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193 rts ; return to caller
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194 interpret1 ldd ,x ; are we at the end of the program?
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195 beq interpret4 ; brif so - bail out
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196 stx curline ; save pointer to current line
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197 leax 3,x ; set input pointer one before the start of the line text
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198 interpret2 stx inputptr
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199 interpret3 jsr nextchar ; fetch first character of next statement
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200 beq interpret ; brif end of statement - do the next statement dance
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201 tsta ; set flags properly for token
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202 lbpl cmd_let ; brif no command - do assignment (LET command is optional)
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203 ldx #primaryjump ; point to jump table
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204 anda #0x7f ; lose bit 7
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205 leax a,x ; get half way to the correct offset
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206 ldx a,x ; get the address the other half of the way from here
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207 jsr nextchar ; skip past token and set flags
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208 jsr ,x ; call the routine
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209 bra interpret ; go handle the next statement dance
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210 interpret4 bsr cmd_stop1 ; make sure stack is aligned correctly (will not return)
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211 interpretline clr curline ; blank out current line pointer (for immediate mode)
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212 clr curline+1
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213 leax -1,x ; move back before start of code stream
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214 bra interpret2 ; go interpret this statement and then continue with stuff
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215 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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216 ; Check for character in B and raise a syntax error if not found at current input pointer. If it is found, fetch the
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217 ; next input character.
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218 syncheckb cmpb [inputptr] ; do we have a syntax match?
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219 bne SNERROR ; brif not
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220 jmp nextchar ; return next input character
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221 *pragmapop list