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|
#
# A simple calculator, version 3.
#
class Calculator3
prechigh
nonassoc UMINUS
left '*' '/'
left '+' '-'
preclow
options no_result_var
rule
target : exp
| /* none */ { 0 }
exp : exp '+' exp { val[0] + val[2] }
| exp '-' exp { val[0] - val[2] }
| exp '*' exp { val[0] * val[2] }
| exp '/' exp { val[0] / val[2] }
| '(' exp ')' { val[1] }
| '-' NUMBER =UMINUS { -(val[1]) }
| NUMBER
end
---- header ----
#
# generated by racc
#
require 'calc3.rex'
---- inner ----
---- footer ----
if $stdin.tty? then
puts 'sample calc'
puts '"q" to quit.'
end
calc = Calculator3.new
while true
if $stdin.tty? then
print '>>> '; $stdout.flush
end
str = $stdin.gets.strip
break if /q/i === str
begin
p calc.parse str
rescue ParseError
puts 'parse error'
end
break unless $stdin.tty?
end
|
