92 lines
1.8 KiB
Bash
Executable File
92 lines
1.8 KiB
Bash
Executable File
#!/bin/sh
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# Scheme syntax:
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#
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# ()lrwqicntfexyz
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#
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# ( start list
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# ) end list
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# l lambda
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# r read byte
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# w write byte
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# q quote next byte in the source
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# i byte to int
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# c cons
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# n null
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# t true
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# f false
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# e eq?
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# x user variable (shadowing not allowed)
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# y user variable (shadowing not allowed)
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# z user variable (shadowing not allowed)
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# TODO: free, GC roots, alloc, function pointers, …
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#
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# sh variables:
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#
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# a answer
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# c lexer current char
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# h heap_max
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# t$i heap_type[$i]
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# v$i heap_value[$i]
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# d$i heap_cdr[$i]
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#
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# heap types:
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#
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# type v d
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# P pair ptr ptr
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# N null "_"
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# F free cell ptr
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# I integer int
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# Y symbol hex
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# O lexer "(" mark "_"
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#
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# Note: hex strings must not contain any spaces.
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h=0
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heap_sbrk() { h=$(($h+1)); }
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heap_get_type() { eval a=\$t$1; }
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heap_get_val() { eval a=\$v$1; }
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heap_get_cdr() { eval a=\$d$1; }
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heap_set() { eval t$1=$2; eval v$1=$3; }
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heap_set_pair() { eval t$1=$2; eval v$1=$3; eval d$1=$4; }
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heap_debug() { for heap_debug_i in `seq $h`; do
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printf %s" " $heap_debug_i
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heap_get_type $heap_debug_i; printf %s" " $a
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heap_get_val $heap_debug_i; printf %s" " $a
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heap_get_cdr $heap_debug_i; printf %s\\n $a
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done }
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rlist() {
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rlist_ptr=$h
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heap_sbrk; heap_set $h N _
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rlist_cdr=$h
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heap_get_type $rlist_ptr
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while test $a != O; do
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heap_sbrk; heap_set_pair $h P $rlist_ptr $rlist_cdr
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rlist_cdr=$h
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rlist_ptr=$(($rlist_ptr-1))
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heap_get_type $rlist_ptr
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done
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a=$rlist_cdr
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}
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main() {
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printf '(lxx)' \
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| od -v -A n -t x1 \
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| sed -e 's/^ //' \
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| tr ' ' \\n \
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echo lex:$c
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case "$c" in
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28) heap_sbrk; heap_set $h O _ ;;
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29) rlist ;;
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*) heap_sbrk; heap_set $h Y $c ;;
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esac
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done
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heap_debug)
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}
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if true; then main; exit $?; fi
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