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Contents
# This class contains our logic for parsing
# S-Expressions. They are turned into a
# native Ruby representation like:
# [:def, :something [:lambda, [:a], [:do_something]]]
class Sexpistol
attr_accessor :ruby_keyword_literals, :scheme_compatability
# Parse a string containing an S-Expression into a
# nested set of Ruby arrays
def parse_string(string)
tree = SexpistolParser.new(string).parse
return convert_ruby_keyword_literals(tree) if(@ruby_keyword_literals)
return tree
end
# Convert symbols corresponding to Ruby's keyword literals
# into their literal forms
def convert_ruby_keyword_literals(expression)
return recursive_map(expression) do |x|
case x
when :'nil' then nil
when :'true' then true
when :'false' then false
else x
end
end
end
# Convert nil, true and false into (), #t and #f for compatability
# with Scheme
def convert_scheme_literals(data)
return recursive_map(data) do |x|
case x
when nil then []
when true then :"#t"
when false then :"#f"
else x
end
end
end
# Convert a set of nested arrays back into an S-Expression
def to_sexp(data)
data = convert_scheme_literals(data) if(@scheme_compatability)
if( data.is_a?(Array))
mapped = data.map do |item|
if( item.is_a?(Array))
to_sexp(item)
elsif item.is_a?(String)
# preserve string literal double quoting
item.inspect
else
item.to_s
end
end
"(" + mapped.join(" ") + ")"
else
data.to_s
end
end
private
def recursive_map(data, &block)
if(data.is_a?(Array))
return data.map do |x|
if(x.is_a?(Array))
recursive_map(x, &block)
else
block.call(x)
end
end
else
block.call(data)
end
end
end
Version data entries
11 entries across 11 versions & 1 rubygems