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NotReallyFORTH
class Proc
def prim_call(stack)
forth_arity = self.arity - 1
if stack.size < forth_arity
puts "Buffer underrun"
return stack.clear
end
forth_arity > 0 ? self.call(stack, *stack.pop(forth_arity)) : call(stack)
end
end
stack = []
functions = {}
primitives = {
":" => ->(_, (name, *body)) { functions[name] = body },
"+" => ->(stack, x, y) { stack << (x + y) },
"-" => ->(stack, x, y) { stack << (x - y) },
"*" => ->(stack, x, y) { stack << (x * y) },
"/" => ->(stack, x, y) { stack << (x / y) },
"dup" => ->(stack) { stack << stack.last },
"rot" => ->(stack) { stack[-2..-1] = stack[-2..-1].reverse },
"." => ->(_, x) { puts x },
".S" => ->(stack) { puts "<#{stack.size}> #{stack.join(' ')} " },
".F" => ->(_) { functions.each { |n, b| puts "#{n}: #{b.join(' ')}"} },
"clearstack" => ->(stack) { stack.clear }
}
parse = ->(input, main=true) do
tokens = main ? input.split(/\s+/) : input
return primitives[":"].call(stack, tokens[1..-2]) if tokens.first == ":"
tokens.each do |token|
if (primitive = primitives[token])
primitive.prim_call(stack)
elsif (function = functions[token])
parse.call(function, false)
else
begin
stack << Integer(token)
rescue ArgumentError
puts "Undefined word <<<#{token}>>>"
stack.clear
end
end
end
puts " ok" if main
end
puts <<EOF
NotReallyFORTH
Type 'bye' to exit
EOF
until (input = gets.chomp) == 'bye'
parse.call(input)
end
NotReallyFORTH 0.1
Type 'bye' to exit
4 5
ok
.S
<2> 4 5
ok
+
ok
.S
<1> 9
ok
dup + .
18
ok
1 2 3 rot .S
<3> 1 3 2
ok
clearstack
ok
: square dup * ;
5 square .
25
ok
.F
square: dup *
bye
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