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285
java/expression/Expression.java
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285
java/expression/Expression.java
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package expression;
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import base.Asserts;
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import base.ExtendedRandom;
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import base.Pair;
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import base.TestCounter;
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import expression.common.ExpressionKind;
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import expression.common.Type;
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import java.util.List;
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/**
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* One-argument arithmetic expression over integers.
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*
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* @author Georgiy Korneev (kgeorgiy@kgeorgiy.info)
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*/
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@FunctionalInterface
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@SuppressWarnings("ClassReferencesSubclass")
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public interface Expression extends ToMiniString {
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int evaluate(int x);
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// Tests follow. You may temporarily remove everything til the end.
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Subtract EXAMPLE = new Subtract(
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new Multiply(new Const(2), new Variable("x")),
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new Const(3)
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);
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Type<Integer> TYPE = new Type<>(a -> a, ExtendedRandom::nextInt, int.class);
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ExpressionKind<Expression, Integer> KIND = new ExpressionKind<>(
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TYPE,
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Expression.class,
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List.of(Pair.of("x", new Variable("x"))),
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(expr, variables, values) -> expr.evaluate(values.get(0))
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);
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private static Const c(final int c) {
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return new Const(c);
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}
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@SuppressWarnings({ "PointlessArithmeticExpression", "Convert2MethodRef" })
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static ExpressionTester<?, ?> tester(final TestCounter counter) {
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Asserts.assertEquals(
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"Example toString()",
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"((2 * x) - 3)",
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EXAMPLE.toString()
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);
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Asserts.assertEquals("Example at 5", 7, EXAMPLE.evaluate(5));
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Asserts.assertTrue(
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"Example equals 1",
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new Multiply(new Const(2), new Variable("x")).equals(
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new Multiply(new Const(2), new Variable("x"))
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)
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);
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Asserts.assertTrue(
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"Example equals 2",
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!new Multiply(new Const(2), new Variable("x")).equals(
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new Multiply(new Variable("x"), new Const(2))
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)
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);
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final Variable vx = new Variable("x");
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final Const c1 = c(1);
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final Const c2 = c(2);
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return new ExpressionTester<>(
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counter,
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KIND,
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c -> x -> c,
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(op, a, b) -> x -> op.apply(a.evaluate(x), b.evaluate(x)),
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(a, b) -> a + b,
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(a, b) -> a - b,
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(a, b) -> a * b,
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(a, b) -> a / b
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)
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.basic("10", "10", x -> 10, c(10))
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.basic("x", "x", x -> x, vx)
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.basic("(x + 2)", "x + 2", x -> x + 2, new Add(vx, c(2)))
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.basic("(2 - x)", "2 - x", x -> 2 - x, new Subtract(c(2), vx))
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.basic("(3 * x)", "3 * x", x -> 3 * x, new Multiply(c(3), vx))
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.basic("(x + x)", "x + x", x -> x + x, new Add(vx, vx))
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.basic("(x / -2)", "x / -2", x -> -x / 2, new Divide(vx, c(-2)))
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.basic("(2 + x)", "2 + x", x -> 2 + x, new Add(c(2), vx))
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.basic(
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"((1 + 2) + 3)",
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"1 + 2 + 3",
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x -> 6,
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new Add(new Add(c(1), c(2)), c(3))
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)
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.basic(
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"(1 + (2 + 3))",
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"1 + 2 + 3",
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x -> 6,
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new Add(c(1), new Add(c(2), c(3)))
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)
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.basic(
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"((1 - 2) - 3)",
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"1 - 2 - 3",
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x -> -4,
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new Subtract(new Subtract(c(1), c(2)), c(3))
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)
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.basic(
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"(1 - (2 - 3))",
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"1 - (2 - 3)",
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x -> 2,
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new Subtract(c(1), new Subtract(c(2), c(3)))
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)
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.basic(
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"((1 * 2) * 3)",
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"1 * 2 * 3",
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x -> 6,
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new Multiply(new Multiply(c(1), c(2)), c(3))
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)
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.basic(
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"(1 * (2 * 3))",
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"1 * 2 * 3",
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x -> 6,
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new Multiply(c(1), new Multiply(c(2), c(3)))
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)
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.basic(
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"((10 / 2) / 3)",
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"10 / 2 / 3",
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x -> 10 / 2 / 3,
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new Divide(new Divide(c(10), c(2)), c(3))
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)
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.basic(
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"(10 / (3 / 2))",
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"10 / (3 / 2)",
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x -> 10 / (3 / 2),
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new Divide(c(10), new Divide(c(3), c(2)))
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)
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.basic(
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"(10 * (3 / 2))",
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"10 * (3 / 2)",
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x -> 10 * (3 / 2),
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new Multiply(c(10), new Divide(c(3), c(2)))
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)
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.basic(
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"(10 + (3 - 2))",
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"10 + 3 - 2",
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x -> 10 + (3 - 2),
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new Add(c(10), new Subtract(c(3), c(2)))
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)
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.basic(
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"((x * x) + ((x - 1) / 10))",
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"x * x + (x - 1) / 10",
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x -> x * x + (x - 1) / 10,
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new Add(
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new Multiply(vx, vx),
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new Divide(new Subtract(vx, c(1)), c(10))
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)
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)
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.basic(
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"(x * -1000000000)",
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"x * -1000000000",
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x -> x * -1_000_000_000,
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new Multiply(vx, c(-1_000_000_000))
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)
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.basic("(10 / x)", "10 / x", x -> 10 / x, new Divide(c(10), vx))
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.basic("(x / x)", "x / x", x -> x / x, new Divide(vx, vx))
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.advanced("(2 + 1)", "2 + 1", x -> 2 + 1, new Add(c2, c1))
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.advanced("(x - 1)", "x - 1", x -> x - 1, new Subtract(vx, c1))
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.advanced("(1 * 2)", "1 * 2", x -> 1 * 2, new Multiply(c1, c2))
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.advanced("(x / 1)", "x / 1", x -> x / 1, new Divide(vx, c1))
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.advanced(
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"(1 + (2 + 1))",
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"1 + 2 + 1",
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x -> 1 + 2 + 1,
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new Add(c1, new Add(c2, c1))
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)
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.advanced(
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"(x - (x - 1))",
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"x - (x - 1)",
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x -> x - (x - 1),
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new Subtract(vx, new Subtract(vx, c1))
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)
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.advanced(
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"(2 * (x / 1))",
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"2 * (x / 1)",
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x -> 2 * (x / 1),
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new Multiply(c2, new Divide(vx, c1))
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)
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.advanced(
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"(2 / (x - 1))",
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"2 / (x - 1)",
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x -> 2 / (x - 1),
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new Divide(c2, new Subtract(vx, c1))
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)
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.advanced(
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"((1 * 2) + x)",
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"1 * 2 + x",
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x -> 1 * 2 + x,
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new Add(new Multiply(c1, c2), vx)
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)
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.advanced(
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"((x - 1) - 2)",
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"x - 1 - 2",
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x -> x - 1 - 2,
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new Subtract(new Subtract(vx, c1), c2)
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)
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.advanced(
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"((x / 1) * 2)",
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"x / 1 * 2",
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x -> (x / 1) * 2,
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new Multiply(new Divide(vx, c1), c2)
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)
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.advanced(
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"((2 + 1) / 1)",
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"(2 + 1) / 1",
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x -> (2 + 1) / 1,
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new Divide(new Add(c2, c1), c1)
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)
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.advanced(
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"(1 + (1 + (2 + 1)))",
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"1 + 1 + 2 + 1",
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x -> 1 + 1 + 2 + 1,
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new Add(c1, new Add(c1, new Add(c2, c1)))
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)
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.advanced(
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"(x - ((1 * 2) + x))",
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"x - (1 * 2 + x)",
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x -> x - (1 * 2 + x),
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new Subtract(vx, new Add(new Multiply(c1, c2), vx))
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)
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.advanced(
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"(x * (2 / (x - 1)))",
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"x * (2 / (x - 1))",
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x -> x * (2 / (x - 1)),
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new Multiply(vx, new Divide(c2, new Subtract(vx, c1)))
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)
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.advanced(
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"(x / (1 + (2 + 1)))",
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"x / (1 + 2 + 1)",
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x -> x / (1 + 2 + 1),
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new Divide(vx, new Add(c1, new Add(c2, c1)))
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)
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.advanced(
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"((1 * 2) + (2 + 1))",
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"1 * 2 + 2 + 1",
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x -> 1 * 2 + 2 + 1,
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new Add(new Multiply(c1, c2), new Add(c2, c1))
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)
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.advanced(
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"((2 + 1) - (2 + 1))",
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"2 + 1 - (2 + 1)",
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x -> 2 + 1 - (2 + 1),
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new Subtract(new Add(c2, c1), new Add(c2, c1))
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)
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.advanced(
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"((x - 1) * (x / 1))",
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"(x - 1) * (x / 1)",
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x -> (x - 1) * (x / 1),
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new Multiply(new Subtract(vx, c1), new Divide(vx, c1))
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)
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.advanced(
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"((x - 1) / (1 * 2))",
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"(x - 1) / (1 * 2)",
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x -> (x - 1) / (1 * 2),
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new Divide(new Subtract(vx, c1), new Multiply(c1, c2))
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)
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.advanced(
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"(((x - 1) - 2) + x)",
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"x - 1 - 2 + x",
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x -> x - 1 - 2 + x,
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new Add(new Subtract(new Subtract(vx, c1), c2), vx)
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)
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.advanced(
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"(((1 * 2) + x) - 1)",
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"1 * 2 + x - 1",
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x -> 1 * 2 + x - 1,
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new Subtract(new Add(new Multiply(c1, c2), vx), c1)
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)
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.advanced(
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"(((2 + 1) / 1) * x)",
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"(2 + 1) / 1 * x",
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x -> ((2 + 1) / 1) * x,
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new Multiply(new Divide(new Add(c2, c1), c1), vx)
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)
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.advanced(
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"((2 / (x - 1)) / 2)",
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"2 / (x - 1) / 2",
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x -> 2 / (x - 1) / 2,
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new Divide(new Divide(c2, new Subtract(vx, c1)), c2)
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);
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}
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}
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