(ab)using ruby within treetop(?)
May 8th, 2008 • Uncategorized
rule case_expression
case_keyword SPACE case_exp:expression SPACE
when_expression_list SPACE
else_keyword SPACE else_exp:statement_list SPACE
end_keyword
{
def eval(env = {})
case_val = case_exp.eval(env)
else_val = else_exp.eval(env)
Kernel.eval <<-CASE_STMT
lambda do
case #{case_val.is_a?(String) ? "'#{case_val}'" : case_val}
#{ruby_when_expressions(env)}
else #{else_val.is_a?(String) ? "'#{else_val}'" : else_val}
end
end [] # call this lambda immediately
CASE_STMT
end
def ruby_when_expressions(env = {})
when_expression_list.eval(env).inject('') do |ruby, e|
# possible string values have been wrapped in '' already
ruby << "when #{e[:condition]} then #{e[:expression]} "
end
end
}
end