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Correct offset error for keyword table lookup
author William Astle <lost@l-w.ca>
date Sun, 07 Jan 2024 20:35:51 -0700
parents 8770e6f977c3
children ac183a519439
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 ; This is the overall parsing package. This is responsible for converting program text into the internal byte code and
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5 ; reporting any syntax errors and anything else reasonably detectable at parse time without having overly complicated
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6 ; code analysis.
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7 ;
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8 ; This is a recursive descent parser.
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9 ;
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10 ; Entry:
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11 ; X Points to the text to encode
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12 ; B Nonzero to prevent generating any output (error check/length calculation only)
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13 ;
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14 ; Exit:
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15 ; U Points to the encoded line
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16 ; D Length of the encoded line
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17 ; CC.C clear
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18
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19 ; Error Exit:
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20 ; B Error code
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21 ; U Offset to error input
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22 ; CC.C set
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23 parse stb parse_noout ; save no-output flag
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24 leay ,x ; save input pointer in a less useful register
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25 ldu freestart ; point to start of free memory where we will build the output
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26 pshs u ; save original free memory location
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27 parse_nextstmt jsr parse_nexttok ; fetch the next token, return type in D
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28 bcc parse0 ; brif we succeeded in parsing a token
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29 parse_error puls u ; restore original free memory location - deallocate any encoding
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30 stu freestart
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31 ldu parse_tokenst ; get start location we started parsing the token at
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32 rts ; return error condition
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33 parse0 ldx #parse_stmtjump ; point to jump table for token type handler
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34 abx ; offset to handler address
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35 abx
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36 jsr [,x] ; call handler
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37 bcs parse_error ; brif handler flagged error
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38 jsr parse_curtoken ; get the token we terminated on
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39 cmpb #token_eot ; end of input?
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40 bne parse1 ; brif not
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41 ldb #bc_eol ; stash an end of line op
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42 bsr parse_write
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43 bcs parse_error ; brif we errored out writing to the result (OM?)
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44 tfr u,d ; calculate the length of the result
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45 subd ,s
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46 puls u,pc ; get pointer to start of encoded result and return (C is already clear)
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47 parse1 cmpb #token_stmtsep ; statement separator?
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48 beq parse_nextstmt ; brif so - do another statement
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49 cmpb #token_apos ; ' token?
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50 beq parse0 ; brif so - parse it as a new statement
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51 comb ; set C for error
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52 ldb #err_sn ; raise syntax error
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53 bra parse_error
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54 parse_write lda parse_noout ; are we doing output?
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55 beq parse_write0 ; brif so
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56 leau 1,u ; just count up the output and don't do anything
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57 rts
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58 parse_write0 leax -stackheadroom,s ; calculate bottom of stack with headroom
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59 cmpx freestart ; did the stack run into the end of the output?
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60 bhs parse_write1 ; brif not - we're good
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61 ldb #err_om ; raise out of memory error, C already set from comparison
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62 rts
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63 parse_write1 stb ,u+ ; save output byte
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64 stu freestart ; save new to of used memory
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65 parse_noop rts ; return all clear - C clear from comparison above
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66 parse_curtoken ldb parse_curtok ; fetch token code of current token
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67 rts
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68 parse_tokerr comb ; flag error - unexpected token
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69 ldb #err_sn ; raise syntax error
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70 rts
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71 parse_nextchar lda ,y ; at end of input already?
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72 beq parse_curchar ; brif so
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73 leay 1,y ; move to next input character
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74 parse_curchar lda ,y ; fetch input character
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75 rts
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76 parse_nexttok bsr parse_curchar ; fetch current input
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77 beq parse_nexttok1 ; brif end of input
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78 parse_nexttok0 cmpa #0x20 ; space?
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79 bne parse_nexttok2 ; brif not
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80 bsr parse_nextchar ; eat the space
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81 bne parse_nexttok0 ; brif not end of input
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82 parse_nexttok1 ldb #token_eot ; flag end of input
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83 bra parse_nexttok6 ; go return it
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84 parse_nexttok2 sty parse_tokenst ; save start of current token after skipping spaces
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85 bsr parse_toupper ; make sure we have upper case letters for matching
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86 ldx #parse_wt ; point to keyword parsing table
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87 bsr parse_wordtab ; go see if we have a match in the keyword table
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88 bcc parse_nexttok6 ; brif we do - return it
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89 ldy parse_tokenst ; return to the start of the token - pointer probably clobbered
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90 bsr parse_curchar ; get back input character (may have been clobbered)
121
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91 cmpa #'. ; leading decimal?
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92 beq parse_nexttok3 ; brif so - parse number
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93 cmpa #'0 ; is it a digit
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94 blo parse_nexttok10 ; brif not
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95 cmpa #'9 ; is it still a digit?
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96 bhi parse_nexttok10 ; brif not
121
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97 parse_nexttok3 jmp parse_number ; go parse a number
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98 parse_nexttok6 stb parse_curtok ; save token type
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99 leay 1,y ; eat the input character
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100 clra ; clear C to indicate no error (and clear Z also)
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101 rts
124
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102 parse_nexttok10 cmpa #'A ; is it alpha?
121
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103 blo parse_nexttok11 ; brif not
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104 cmpa #'Z ; is it still alpha?
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105 bls parse_nexttok12 ; brif so
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106 parse_nexttok11 comb ; flag error - unrecognized token
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107 ldb #token_error
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108 rts
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109 parse_nexttok12 bsr parse_nextcharu ; fetch next input character
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110 cmpa #'0 ; is it alphanumeric?
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111 blo parse_nexttok13 ; brif not
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112 cmpa #'9 ; is it numeric?
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113 bls parse_nexttok12 ; brif so - keep skipping it
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114 cmpa #'A ; is it alpha?
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115 blo parse_nexttok13 ; brif not
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116 cmpa #'Z ; is it still alpha?
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117 bls parse_nexttok12 ; brif so - keep skipping it
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118 parse_nexttok13 tfr y,d ; calculate length of identifier
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119 subd parse_tokenst
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120 std val0+val.strlen ; save it for reference
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121 ldb #token_ident ; indicate an identifier (variable name, etc.)
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122 rts ; return result (C will be clear from SUBD above)
121
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123 parse_nextcharu bsr parse_nextchar ; fetch next input character
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124 beq parse_toupper0 ; brif end of input
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125 parse_toupper cmpa #'a ; is it lower case alpha?
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126 blo parse_toupper0 ; brif not
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127 cmpa #'z ; is it still lower case alpha?
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128 bhi parse_toupper0 ; brif not
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129 suba #0x20 ; adjust to upper case alpha
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130 parse_toupper0 rts ; Z only set here if input was zero entering from parse_nextcharu
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131 ; This routine parses tokens using the table at parse_wordtab. The table is structured as follows:
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132 ;
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133 ; * two bytes which contain the length of the table less the two bytes for this length value
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134 ; * a sequence of entries consisting of a single byte matching character and a token code followed
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135 ; by an optional sub table, structured exactly the same way.
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136 ;
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137 ; The optional subtable will be present if the token code is token_eot
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138 ;
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139 ; If the character match is negative, it means a lookahead failed. The negative value is the number
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140 ; of characters to unget and the token code is the token value to return. No other entries after this
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141 ; in a table will be considered since thie negative match is a global match.
121
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142 ;
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143 ; When a token_eot match is found, if there are no further characters in the input, the match is
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144 ; determined to be invalid and processing continues with the next entry.
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145 parse_wordtab0 leas 3,s ; clean up stack for sub table handling
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146 parse_wordtab pshs a,x ; save input character and start of table
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147 ldd ,x++ ; get length of this table
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148 addd 1,s ; calculate the address of the end of the table
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149 std 1,s ; save end address for comparison later
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150 lda ,s ; get back input character
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151 parse_wordtab1 ldb 1,x ; fetch token code for this entry
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152 cmpa ,x++ ; does this entry match?
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153 bne parse_wordtab4 ; brif not
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154 cmpb #token_eot ; is it indicating a sub table?
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155 bne parse_wordtab6 ; brif not
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156 bsr parse_nextcharu ; fetch next input character (for sub table match)
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157 bne parse_wordtab0 ; brif we are going to check the sub table
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158 parse_wordtab2 ldd ,x++ ; fetch length of sub table
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159 leax d,x ; move past sub table
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160 parse_wordtab3 lda ,s ; get back input character
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161 cmpx 1,s ; are we at the end of the table?
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162 blo parse_wordtab1 ; brif not - check another entry
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163 comb ; indicate no match
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164 puls a,x,pc ; clean up stack and return
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165 parse_wordtab4 lda -2,x ; get the match character
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166 bmi parse_wordtab5 ; brif negative - lookahead fail
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167 cmpb #token_eot ; is there a sub table to skip?
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168 beq parse_wordtab2 ; brif so - skip sub table
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169 bra parse_wordtab3 ; otherwise just move to the next entry
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170 parse_wordtab5 leay a,y ; move back the specified number of characters
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171 parse_wordtab6 clra ; clear C to indicate a match
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172 puls a,x,pc ; clean up stack and return
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173 parse_number jmp parse_tokerr
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174 ; Parse tokens - define them in order using the macro parse_tokdef
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175 *pragmapush list
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176 *pragma nolist
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177 parse_toknum set 0
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178 parse_tokdef macro noexpand
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179 \1 equ parse_toknum
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180 parse_toknum set parse_toknum+1
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181 fdb \2
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182 endm
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183 *pragmapop list
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184 parse_stmtjump parse_tokdef token_error,parse_tokerr
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185 parse_tokdef token_eot,parse_noop
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186 parse_tokdef token_lt,parse_noop
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187 parse_tokdef token_le,parse_noop
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188 parse_tokdef token_gt,parse_noop
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189 parse_tokdef token_ge,parse_noop
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190 parse_tokdef token_eq,parse_noop
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191 parse_tokdef token_ne,parse_noop
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192 parse_tokdef token_reltrue,parse_noop // always true relational operator
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193 parse_tokdef token_stmtsep,parse_noop
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194 parse_tokdef token_apos,parse_rem
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195 parse_tokdef token_special,parse_noop
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196 parse_tokdef token_bang,parse_noop
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197 parse_tokdef token_hash,parse_noop
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198 parse_tokdef token_dollar,parse_noop
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199 parse_tokdef token_percent,parse_noop
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200 parse_tokdef token_amp,parse_noop
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201 parse_tokdef token_oparen,parse_noop
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202 parse_tokdef token_cparen,parse_noop
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203 parse_tokdef token_star,parse_noop
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204 parse_tokdef token_plus,parse_noop
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205 parse_tokdef token_comma,parse_noop
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206 parse_tokdef token_minus,parse_noop
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207 parse_tokdef token_slash,parse_noop
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208 parse_tokdef token_semi,parse_noop
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209 parse_tokdef token_at,parse_noop
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210 parse_tokdef token_exp,parse_noop
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211 parse_tokdef token_ident,parse_noop
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212 parse_tokdef token_rem,parse_noop
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213 parse_tokdef token_return,parse_noop
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214 parse_tokdef token_run,parse_noop
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215 parse_tokdef token_data,parse_noop
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216 parse_tokdef token_else,parse_noop
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217 parse_tokdef token_end,parse_noop
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218 parse_tokdef token_stop,parse_noop
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219 parse_tokdef token_sub,parse_noop
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220 parse_tokdef token_let,parse_noop
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221 parse_tokdef token_list,parse_noop
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222 parse_tokdef token_new,parse_noop
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223 parse_tokdef token_not,parse_noop
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224 parse_tokdef token_print,parse_noop
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225 parse_tokdef token_pop,parse_noop
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226 parse_tokdef token_to,parse_noop
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227 parse_tokdef token_and,parse_noop
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228 parse_tokdef token_or,parse_noop
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229 parse_tokdef token_go,parse_noop
123
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230 parse_tokdef token_as,parse_noop
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231 parse_tokdef token_asc,parse_noop
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232 parse_rem rts
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233
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234 *pragmapop list