# Mu - shell/parse.mu

https://github.com/akkartik/mu/blob/main/shell/parse.mu

      1 fn parse-input tokens: (addr stream cell), out: (addr handle cell), trace: (addr trace) {
      2   rewind-stream tokens
      3   var empty?/eax: boolean <- stream-empty? tokens
      4   compare empty?, 0/false
      5   {
      6     break-if-=
      7     error trace, "nothing to parse"
      8     return
      9   }
     10   var close-paren?/eax: boolean <- copy 0/false
     11   var dummy?/ecx: boolean <- copy 0/false
     12   close-paren?, dummy? <- parse-sexpression tokens, out, trace
     13   {
     14     compare close-paren?, 0/false
     15     break-if-=
     16     error trace, "')' is not a valid expression"
     17     return
     18   }
     19   {
     20     var empty?/eax: boolean <- stream-empty? tokens
     21     compare empty?, 0/false
     22     break-if-!=
     23     error trace, "unexpected tokens at end; only type in a single expression at a time"
     24   }
     25 }
     26
     27 # return values:
     28 #   unmatched close-paren encountered?
     29 #   dot encountered? (only used internally by recursive calls)
     30 fn parse-sexpression tokens: (addr stream cell), _out: (addr handle cell), trace: (addr trace) -> _/eax: boolean, _/ecx: boolean {
     31   trace-text trace, "read", "parse"
     32   trace-lower trace
     33   var curr-token-storage: cell
     34   var curr-token/ecx: (addr cell) <- address curr-token-storage
     35   var empty?/eax: boolean <- stream-empty? tokens
     36   compare empty?, 0/false
     37   {
     38     break-if-=
     39     error trace, "end of stream; never found a balancing ')'"
     40     return 1/true, 0/false
     41   }
     42   read-from-stream tokens, curr-token
     43   $parse-sexpression:type-check: {
     44     # single quote -> parse as list with a special car
     45     var quote-token?/eax: boolean <- quote-token? curr-token
     46     compare quote-token?, 0/false
     47     {
     48       break-if-=
     49       var out/edi: (addr handle cell) <- copy _out
     50       allocate-pair out
     51       var out-addr/eax: (addr cell) <- lookup *out
     52       var left-ah/edx: (addr handle cell) <- get out-addr, left
     53       new-symbol left-ah, "'"
     54       var right-ah/edx: (addr handle cell) <- get out-addr, right
     55       var close-paren?/eax: boolean <- copy 0/false
     56       var dot?/ecx: boolean <- copy 0/false
     57       close-paren?, dot? <- parse-sexpression tokens, right-ah, trace
     58       return close-paren?, dot?
     59     }
     60     # dot -> return
     61     var dot?/eax: boolean <- dot-token? curr-token
     62     compare dot?, 0/false
     63     {
     64       break-if-=
     65       trace-higher trace
     66       return 0/false, 1/true
     67     }
     68     # not bracket -> parse atom
     69     var bracket-token?/eax: boolean <- bracket-token? curr-token
     70     compare bracket-token?, 0/false
     71     {
     72       break-if-!=
     73       parse-atom curr-token, _out, trace
     74       break $parse-sexpression:type-check
     75     }
     76     # open paren -> parse list
     77     var open-paren?/eax: boolean <- open-paren-token? curr-token
     78     compare open-paren?, 0/false
     79     {
     80       break-if-=
     81       var curr/esi: (addr handle cell) <- copy _out
     82       allocate-pair curr
     83       var curr-addr/eax: (addr cell) <- lookup *curr
     84       var left/edx: (addr handle cell) <- get curr-addr, left
     85       {
     86         var close-paren?/eax: boolean <- copy 0/false
     87         var dot?/ecx: boolean <- copy 0/false
     88         close-paren?, dot? <- parse-sexpression tokens, left, trace
     89         {
     90           compare dot?, 0/false
     91           break-if-=
     92           error trace, "'.' cannot be at the start of a list"
     93           return 1/true, dot?
     94         }
     95         compare close-paren?, 0/false
     96         break-if-!=
     97         var curr-addr/eax: (addr cell) <- lookup *curr
     98         curr <- get curr-addr, right
     99         var tmp-storage: (handle cell)
    100         var tmp/edx: (addr handle cell) <- address tmp-storage
    101         $parse-sexpression:list-loop: {
    102           var close-paren?/eax: boolean <- copy 0/false
    103           var dot?/ecx: boolean <- copy 0/false
    104           close-paren?, dot? <- parse-sexpression tokens, tmp, trace
    105           # '.' -> clean up right here and return
    106           compare dot?, 0/false
    107           {
    108             break-if-=
    109             parse-dot-tail tokens, curr, trace
    110             return 0/false, 0/false
    111           }
    112           allocate-pair curr
    113           # ')' -> return
    114           compare close-paren?, 0/false
    115           break-if-!=
    116           var curr-addr/eax: (addr cell) <- lookup *curr
    117           var left/ecx: (addr handle cell) <- get curr-addr, left
    118           copy-object tmp, left
    119           #
    120           curr <- get curr-addr, right
    121           loop
    122         }
    123       }
    124       break $parse-sexpression:type-check
    125     }
    126     # close paren -> return
    127     var close-paren?/eax: boolean <- close-paren-token? curr-token
    128     compare close-paren?, 0/false
    129     {
    130       break-if-=
    131       trace-higher trace
    132       return 1/true, 0/false
    133     }
    134     # otherwise abort
    135     var stream-storage: (stream byte 0x40)
    136     var stream/edx: (addr stream byte) <- address stream-storage
    137     write stream, "unexpected token "
    138     var curr-token-data-ah/eax: (addr handle stream byte) <- get curr-token, text-data
    139     var curr-token-data/eax: (addr stream byte) <- lookup *curr-token-data-ah
    140     rewind-stream curr-token-data
    141     write-stream stream, curr-token-data
    142     trace trace, "error", stream
    143   }
    144   trace-higher trace
    145   return 0/false, 0/false
    146 }
    147
    148 fn parse-atom _curr-token: (addr cell), _out: (addr handle cell), trace: (addr trace) {
    149   trace-text trace, "read", "parse atom"
    150   var curr-token/ecx: (addr cell) <- copy _curr-token
    151   var curr-token-data-ah/eax: (addr handle stream byte) <- get curr-token, text-data
    152   var _curr-token-data/eax: (addr stream byte) <- lookup *curr-token-data-ah
    153   var curr-token-data/esi: (addr stream byte) <- copy _curr-token-data
    154   trace trace, "read", curr-token-data
    155   # number
    156   var number-token?/eax: boolean <- number-token? curr-token
    157   compare number-token?, 0/false
    158   {
    159     break-if-=
    160     rewind-stream curr-token-data
    161     var _val/eax: int <- parse-decimal-int-from-stream curr-token-data
    162     var val/ecx: int <- copy _val
    163     var val-float/xmm0: float <- convert val
    164     allocate-number _out
    165     var out/eax: (addr handle cell) <- copy _out
    166     var out-addr/eax: (addr cell) <- lookup *out
    167     var dest/edi: (addr float) <- get out-addr, number-data
    168     copy-to *dest, val-float
    169     {
    170       var stream-storage: (stream byte 0x40)
    171       var stream/ecx: (addr stream byte) <- address stream-storage
    172       write stream, "=> number "
    173       print-number out-addr, stream, 0/no-trace
    174       trace trace, "read", stream
    175     }
    176     return
    177   }
    178   # default: copy either to a symbol or a stream
    179   # stream token -> literal
    180   var stream-token?/eax: boolean <- stream-token? curr-token
    181   compare stream-token?, 0/false
    182   {
    183     break-if-=
    184     allocate-stream _out
    185   }
    186   compare stream-token?, 0/false
    187   {
    188     break-if-!=
    189     allocate-symbol _out
    190   }
    191   # copy token data
    192   var out/eax: (addr handle cell) <- copy _out
    193   var out-addr/eax: (addr cell) <- lookup *out
    194   var curr-token-data-ah/ecx: (addr handle stream byte) <- get curr-token, text-data
    195   var dest-ah/edx: (addr handle stream byte) <- get out-addr, text-data
    196   copy-object curr-token-data-ah, dest-ah
    197   {
    198     var stream-storage: (stream byte 0x40)
    199     var stream/ecx: (addr stream byte) <- address stream-storage
    200     write stream, "=> symbol "
    201     print-symbol out-addr, stream, 0/no-trace
    202     trace trace, "read", stream
    203   }
    204 }
    205
    206 fn parse-dot-tail tokens: (addr stream cell), _out: (addr handle cell), trace: (addr trace) {
    207   var out/edi: (addr handle cell) <- copy _out
    208   var close-paren?/eax: boolean <- copy 0/false
    209   var dot?/ecx: boolean <- copy 0/false
    210   close-paren?, dot? <- parse-sexpression tokens, out, trace
    211   compare close-paren?, 0/false
    212   {
    213     break-if-=
    214     error trace, "'. )' makes no sense"
    215     return
    216   }
    217   compare dot?, 0/false
    218   {
    219     break-if-=
    220     error trace, "'. .' makes no sense"
    221     return
    222   }
    223   #
    224   var dummy: (handle cell)
    225   var dummy-ah/edi: (addr handle cell) <- address dummy
    226   close-paren?, dot? <- parse-sexpression tokens, dummy-ah, trace
    227   compare close-paren?, 0/false
    228   {
    229     break-if-!=
    230     error trace, "cannot have multiple expressions between '.' and ')'"
    231     return
    232   }
    233   compare dot?, 0/false
    234   {
    235     break-if-=
    236     error trace, "cannot have two dots in a single list"
    237     return
    238   }
    239 }