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|
(types.ps) run
(reader.ps) run
% read
/_readline { print flush (%stdin) (r) file 99 string readline } def
/READ {
/str exch def
str read_str
} def
% eval
/eval_ast { 2 dict begin
/env exch def
/ast exch def
%(eval_ast: ) print ast ==
ast _symbol? { %if symbol
env ast known {
env ast get
}{
(') ast pr_str (' not found)
concatenate concatenate throw
} ifelse
}{ ast _list? { %elseif list
[
ast {
env EVAL
} forall
]
}{ % else
ast
} ifelse } ifelse
end } def
/EVAL { 3 dict begin
/env exch def
/ast exch def
%(EVAL: ) print ast ==
ast _list? not { %if not a list
ast env eval_ast
}{ %else apply the list
/el ast env eval_ast def
el _rest el _first % stack: ast function
exec % apply function to args
} ifelse
end } def
% print
/PRINT {
true _pr_str
} def
% repl
/repl_env <<
(+) { dup 0 get exch 1 get add }
(-) { dup 0 get exch 1 get sub }
(*) { dup 0 get exch 1 get mul }
(/) { dup 0 get exch 1 get idiv }
>> def
/REP { READ repl_env EVAL PRINT } def
{ % loop
(user> ) _readline
not { exit } if % exit if EOF
{ %try
REP print (\n) print
} stopped {
(Error: ) print
get_error_data false _pr_str print (\n) print
$error /newerror false put
$error /errorinfo null put
clear
cleardictstack
} if
} bind loop
(\n) print % final newline before exit for cleanliness
quit
|
