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|
(in reader\n) print
/token_delim (;,"` \n{}\(\)[]) def
/token_number (0123456789-) def
% read_number: read a single number from string/idx
% string idx -> read_number -> number string new_idx
/read_number {
%(in read_number\n) print
/idx exch def
/str exch def
/start idx def
/cnt 0 def
{ % loop
idx str length ge { exit } if % EOF, break loop
/ch str idx get def % current character
ch 48 ge ch 57 le and 45 ch eq or { %if number
/cnt cnt 1 add def
}{ % else
exit
} ifelse
/idx idx 1 add def % increment idx
} loop
str start cnt getinterval cvi % the matched number
str idx % return: number string new_idx
} def
% read_symbol: read a single symbol from string/idx
% string idx -> read_symbol -> name string new_idx
/read_symbol {
%(in read_symbol\n) print
/idx exch def
/str exch def
/start idx def
/cnt 0 def
{ % loop
idx str length ge { exit } if % EOF, break loop
/ch str idx 1 getinterval def
token_delim ch search { % if token delimeter
pop pop pop exit
}{ % else not a delim
pop
/cnt cnt 1 add def
} ifelse
/idx idx 1 add def % increment idx
} loop
str start cnt getinterval cvn % the matched symbol
str idx % return: symbol string new_idx
} def
% read_string: read a single string from string/idx
% string idx -> read_string -> new_string string new_idx
/read_string {
%(in read_string\n) print
/idx exch 1 add def
/str exch def
/start idx def
/cnt 0 def
{ % loop
idx str length ge { %if EOF
(unexpected EOF reading string)
throw
} if
/ch str idx get def % current character
/idx idx 1 add def
ch 34 eq { exit } if % '"' is end of string
/cnt cnt 1 add def
} loop
str start cnt getinterval % the matched string
str idx % return: new_string string new_idx
} def
% read_atom: read a single atom from string/idx
% string idx -> read_atom -> int string new_idx
/read_atom {
%(in read_atom\n) print
/idx exch def
/str exch def
str length idx le { % ifelse
exit % EOF
}{
/ch str idx get def % current character
%ch 48 ge ch 57 le and 45 ch eq or { %if number
ch 48 ge ch 57 le and { %if number
str idx read_number
}{ ch 34 eq { %elseif double-quote
str idx read_string
}{
str idx read_symbol
/idx exch def pop
dup /nil eq { %if nil
pop null str idx
}{ dup /true eq { %elseif true
pop true str idx
}{ dup /false eq { %elseif false
pop false str idx
}{ %else
str idx % return the original symbol/name
} ifelse } ifelse } ifelse
} ifelse } ifelse
}ifelse
% return: atom string new_idx
} def
% read_list: read a single list from string/idx
% string idx -> read_list -> list string new_idx
/read_list {
%(in read_list\n) print
/idx exch 1 add def
/str exch def
[
{ % loop
str idx read_spaces /idx exch def pop
str length idx le { %if EOF
(unexpected EOF reading list)
throw
} if
/ch str idx get def % current character
ch 41 eq { exit } if % ')' is end of list
str idx read_form /idx exch def pop
} loop
]
str idx 1 add
} def
% read_spaces: advance idx to the first non-whitespace
% string idx -> read_form -> string new_idx
/read_spaces {
%(in read_spaces\n) print
/idx exch def
/str exch def
{ % loop
str length idx le { exit } if % EOF, break loop
/ch str idx get def % current character
% if not whitespace then exit
ch 32 ne ch 10 ne ch 44 ne and and { exit } if
/idx idx 1 add def % increment idx
} loop
str idx % return: string new_idx
} def
% read_form: read the next form from string start at idx
% string idx -> read_form -> ast string new_idx
/read_form {
%(in read_form\n) print
read_spaces
/idx exch def
/str exch def
idx str length ge { exit } if % EOF, break loop
/ch str idx get def % current character
ch 40 eq { %if (
str idx read_list
}{ ch 91 eq { %elseif [
(unexpected '[') throw
}{ ch 93 eq { %elseif ]
(unexpected ']') throw
}{ % else
str idx read_atom
} ifelse } ifelse } ifelse
%(stack vvv\n) print
%pstack
%(stack ^^^\n) print
% return: ast string new_idx
} def
% string -> read_str -> ast
/read_str {
%(in read_str\n) print
0 % current index into the string
read_form
pop pop % drop the string, idx. return: ast
} def
|
