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defmodule ElixirMathParser do
@moduledoc """
Documentation for `ElixirMathParser`.
"""
defp reduce_to_value({:int, _line, value}, _state) do
{:ok, value}
end
defp reduce_to_value({:atom, _line, atom}, state) do
if !Map.has_key?(state, atom) do
{:error, "value not found for " <> to_string(atom)}
else
{:ok, state[atom]}
end
end
defp reduce_to_value({:add_op, lhs, rhs}, state) do
{:ok, op1} = reduce_to_value(lhs, state)
{:ok, op2} = reduce_to_value(rhs, state)
{:ok, op1 + op2}
end
defp reduce_to_value({:sub_op, lhs, rhs}, state) do
{:ok, op1} = reduce_to_value(lhs, state)
{:ok, op2} = reduce_to_value(rhs, state)
{:ok, op1 - op2}
end
defp reduce_to_value({:mul_op, lhs, rhs}, state) do
{:ok, op1} = reduce_to_value(lhs, state)
{:ok, op2} = reduce_to_value(rhs, state)
{:ok, op1 / op2}
end
defp reduce_to_value({:div_op, lhs, rhs}, state) do
{:ok, op1} = reduce_to_value(lhs, state)
{:ok, op2} = reduce_to_value(rhs, state)
{:ok, op1 / op2}
end
defp evaluate_tree([{:assign, {:atom, _line, lhs}, rhs} | tail], state) do
{:ok, rhs_value} = reduce_to_value(rhs, state)
evaluate_tree(tail, Map.merge(state, %{lhs => rhs_value}))
end
defp evaluate_tree([], state) do
state
end
def process_tree(tree) do
evaluate_tree(tree, %{})
end
def parse_file(filename) do
text = File.read!(filename)
{:ok, tokens, _line} = :elixir_math_parser_lexer.string(String.to_charlist(text))
{:ok, tree} = :elixir_math_parser.parse(tokens)
process_tree(tree)
end
end
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