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90 lines
1.8 KiB
90 lines
1.8 KiB
#! /usr/bin/env crystal run
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require "./readline"
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require "./reader"
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require "./printer"
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require "./types"
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# Note:
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# Employed downcase names because Crystal prohibits uppercase names for methods
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def eval_error(msg)
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raise Mal::EvalException.new msg
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end
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def num_func(func)
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-> (args : Array(Mal::Type)) {
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x, y = args[0].unwrap, args[1].unwrap
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eval_error "invalid arguments" unless x.is_a?(Int32) && y.is_a?(Int32)
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Mal::Type.new func.call(x, y)
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}
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end
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$repl_env = {
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"+" => num_func(->(x : Int32, y : Int32){ x + y }),
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"-" => num_func(->(x : Int32, y : Int32){ x - y }),
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"*" => num_func(->(x : Int32, y : Int32){ x * y }),
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"/" => num_func(->(x : Int32, y : Int32){ x / y }),
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} of String => Mal::Func
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def eval_ast(a, env)
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return a.map{|n| eval(n, env) as Mal::Type} if a.is_a? Mal::List
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return a unless a
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ast = a.unwrap
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case ast
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when Mal::Symbol
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if env.has_key? ast.str
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env[ast.str]
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else
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eval_error "'#{ast.str}' not found"
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end
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when Mal::List
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ast.each_with_object(Mal::List.new){|n, l| l << eval(n, env)}
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when Mal::Vector
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ast.each_with_object(Mal::Vector.new){|n, l| l << eval(n, env)}
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when Mal::HashMap
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ast.each{|k, v| ast[k] = eval(v, env)}
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else
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ast
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end
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end
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def read(str)
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read_str str
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end
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def eval(t, env)
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Mal::Type.new case ast = t.unwrap
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when Mal::List
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eval_error "empty list" if ast.empty?
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f = eval_ast(ast.first, env)
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ast.shift(1)
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args = eval_ast(ast, env)
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if f.is_a?(Mal::Func)
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f.call(args)
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else
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eval_error "expected function symbol as the first symbol of list"
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end
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else
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eval_ast(t, env)
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end
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end
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def print(result)
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pr_str(result, true)
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end
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def rep(str)
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print(eval(read(str), $repl_env))
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end
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while line = my_readline("user> ")
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begin
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puts rep(line)
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rescue e
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STDERR.puts e
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end
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end
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