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Contents
# frozen_string_literal: true
require_relative 'calc_lexer'
require_relative 'calc_ast_builder'
def print_title(aTitle)
puts aTitle
puts '=' * aTitle.size
end
def print_tree(aTitle, aParseTree)
# Let's create a parse tree visitor
visitor = Rley::ParseTreeVisitor.new(aParseTree)
# Now output formatted parse tree
print_title(aTitle)
renderer = Rley::Formatter::Asciitree.new($stdout)
renderer.render(visitor)
puts ''
end
# Parse the input expression in command-line
if ARGV.empty?
my_name = File.basename(__FILE__)
msg = <<-END_MSG
Demo calculator that prints:
- The Concrete and Abstract Syntax Trees of the math expression.
- The result of the math expression.
Command-line syntax:
ruby #{my_name} "arithmetic expression"
where:
the arithmetic expression is enclosed between double quotes (")
Examples:
ruby #{my_name} "2 * 3 + (1 + 3 ** 2)"
ruby #{my_name} "cos(PI/2) + sqrt(1 + 1)"
END_MSG
puts msg
exit(1)
end
puts ARGV[0]
# Create a Rley facade object
engine = Rley::Engine.new
########################################
# Step 1. Load a grammar for calculator
require_relative 'calc_grammar'
engine.use_grammar(CalcGrammar)
lexer = CalcLexer.new(ARGV[0])
result = engine.parse(lexer.tokens)
unless result.success?
# Stop if the parse failed...
puts "Parsing of '#{ARGV[0]}' failed"
puts "Reason: #{result.failure_reason.message}"
exit(1)
end
# Generate a concrete syntax parse tree from the parse result
cst_ptree = engine.convert(result)
print_tree('Concrete Syntax Tree (CST)', cst_ptree)
# Generate an abstract syntax parse tree from the parse result
engine.configuration.repr_builder = CalcASTBuilder
ast_ptree = engine.convert(result)
print_tree('Abstract Syntax Tree (AST)', ast_ptree)
# Now perform the computation of math expression
root = ast_ptree.root
print_title('Result:')
puts root.interpret.to_s # Output the expression result
# End of file
Version data entries
15 entries across 15 versions & 1 rubygems