95 lines
3.0 KiB
C#
95 lines
3.0 KiB
C#
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using System.Reflection;
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using static System.Reflection.BindingFlags;
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namespace InnovEnergy.Lib.Utils;
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public static class Operators
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{
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public static Func<T, T, T> CreateBinaryOpForProps<T>(this String op)
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{
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var methodName = GetMethodNameForBinaryOp(op);
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var props = typeof(T)
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.GetProperties(Instance | Public)
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.Where(p => p.CanWrite)
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.Select(p =>
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(
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prop: p,
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op: GetOpMethod(methodName, p.PropertyType) ??
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throw new ArgumentException($"Type {p.PropertyType.Name} " +
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$"of property {p.Name} " +
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$"has no suitable {op} operator defined."))
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)
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.ToArray();
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var ctr = typeof(T).GetConstructors().FirstOrDefault(c => c.GetParameters().Length == 0);
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if (ctr is null)
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throw new ArgumentException($"Type {typeof(T).Name} has no suitable parameterless constructor.");
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T Op(T left, T right)
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{
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// TODO: make this faster/nicer using Expression API (low prio)
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var result = ctr.Invoke(null);
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foreach (var (p, m) in props)
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{
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var l = p.GetValue(left);
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var r = p.GetValue(right);
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var s = m.Invoke(null, new[] { l, r });
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p.SetValue(result, s);
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}
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return (T) result;
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}
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return Op;
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}
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private static String GetMethodNameForBinaryOp(String op)
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{
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// from https://stackoverflow.com/a/29495075
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return op switch
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{
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"&" => "op_BitwiseAnd",
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"|" => "op_BitwiseOr",
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"+" => "op_Addition",
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"-" => "op_Subtraction",
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"/" => "op_Division",
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"%" => "op_Modulus",
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"*" => "op_Multiply",
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"<<" => "op_LeftShift",
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">>" => "op_RightShift",
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"^" => "op_ExclusiveOr",
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"==" => "op_Equality",
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"!=" => "op_Inequality",
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">" => "op_GreaterThan",
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"<" => "op_LessThan",
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">=" => "op_GreaterThanOrEqual",
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"<=" => "op_LessThanOrEqual",
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_ => throw new ArgumentException("unknown operator", nameof(op))
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};
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}
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private static MethodInfo? GetOpMethod(String? methodName, Type type)
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{
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return type
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.GetMethods(Static | Public)
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.FirstOrDefault(m => m.Name == methodName
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&& m.ReturnType == type
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&& m.IsMonoidOp());
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}
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private static Boolean IsMonoidOp(this MethodInfo m)
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{
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var ps = m.GetParameters();
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return ps.Length == 2 &&
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ps.All(p => p.ParameterType == m.ReturnType);
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}
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}
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