kmath-functions/src/commonMain/kotlin/space/kscience/kmath/functions/AbstractPolynomial.kt

@@ -18,7 +18,7 @@ public interface AbstractPolynomial<C>
 /**
  * Abstraction of ring of polynomials of type [P] over ring of constants of type [C].
  *
- * @param C the type of constants. Polynomials have them as a coefficients in their terms.
+ * @param C the type of constants. Polynomials have them as coefficients in their terms.
  * @param P the type of polynomials.
  */
 @Suppress("INAPPLICABLE_JVM_NAME", "PARAMETER_NAME_CHANGED_ON_OVERRIDE")
@@ -313,10 +313,12 @@ public interface AbstractPolynomialSpace<C, P: AbstractPolynomial<C>> : Ring<P>
 }
 
 /**
- * Abstraction of ring of polynomials of type [P] over ring of constants of type [C].
+ * Abstraction of ring of polynomials of type [P] over ring of constants of type [C]. It also assumes that there is
+ * provided [ring] (of type [A]), that provides constant-wise operations.
  *
- * @param C the type of constants. Polynomials have them as a coefficients in their terms.
+ * @param C the type of constants. Polynomials have them as coefficients in their terms.
  * @param P the type of polynomials.
+ * @param A the type of algebraic structure (precisely, of ring) provided for constants.
  */
 @Suppress("INAPPLICABLE_JVM_NAME")
 public interface AbstractPolynomialSpaceOverRing<C, P: AbstractPolynomial<C>, A: Ring<C>> : AbstractPolynomialSpace<C, P> {

kmath-functions/src/commonMain/kotlin/space/kscience/kmath/functions/AbstractRationalFunction.kt

@@ -20,6 +20,14 @@ public interface AbstractRationalFunction<C, P: AbstractPolynomial<C>> {
     public operator fun component2(): P = denominator
 }
 
+/**
+ * Abstraction of field of rational functions of type [R] with respect to polynomials of type [P] and constants of type
+ * [C].
+ *
+ * @param C the type of constants. Polynomials have them as coefficients in their terms.
+ * @param P the type of polynomials. Rational functions have them as numerators and denominators in them.
+ * @param R the type of rational functions.
+ */ // TODO: Add support of field
 @Suppress("INAPPLICABLE_JVM_NAME", "PARAMETER_NAME_CHANGED_ON_OVERRIDE")
 public interface AbstractRationalFunctionalSpace<C, P: AbstractPolynomial<C>, R: AbstractRationalFunction<C, P>> : Ring<R> {
     // region Constant-integer relation
@@ -508,6 +516,15 @@ public interface AbstractRationalFunctionalSpace<C, P: AbstractPolynomial<C>, R:
     // endregion
 }
 
+/**
+ * Abstraction of field of rational functions of type [R] with respect to polynomials of type [P] and constants of type
+ * [C]. It also assumes that there is provided [ring] (of type [A]), that provides constant-wise operations.
+ *
+ * @param C the type of constants. Polynomials have them as coefficients in their terms.
+ * @param P the type of polynomials. Rational functions have them as numerators and denominators in them.
+ * @param R the type of rational functions.
+ * @param A the type of algebraic structure (precisely, of ring) provided for constants.
+ */ // TODO: Add support of field
 @Suppress("INAPPLICABLE_JVM_NAME")
 public interface AbstractRationalFunctionalSpaceOverRing<C, P: AbstractPolynomial<C>, R: AbstractRationalFunction<C, P>, A: Ring<C>> : AbstractRationalFunctionalSpace<C, P, R> {
 
@@ -593,10 +610,25 @@ public interface AbstractRationalFunctionalSpaceOverRing<C, P: AbstractPolynomia
     // endregion
 }
 
+/**
+ * Abstraction of field of rational functions of type [R] with respect to polynomials of type [P] and constants of type
+ * [C]. It also assumes that there is provided [polynomialRing] (of type [AP]), that provides constant- and
+ * polynomial-wise operations.
+ *
+ * @param C the type of constants. Polynomials have them as coefficients in their terms.
+ * @param P the type of polynomials. Rational functions have them as numerators and denominators in them.
+ * @param R the type of rational functions.
+ * @param AP the type of algebraic structure (precisely, of ring) provided for polynomials.
+ */ // TODO: Add support of field
 @Suppress("INAPPLICABLE_JVM_NAME")
-public interface AbstractRationalFunctionalSpaceOverPolynomialSpace<C, P: AbstractPolynomial<C>, R: AbstractRationalFunction<C, P>, A: Ring<C>> : AbstractRationalFunctionalSpace<C, P, R> {
+public interface AbstractRationalFunctionalSpaceOverPolynomialSpace<
+        C,
+        P: AbstractPolynomial<C>,
+        R: AbstractRationalFunction<C, P>,
+        AP: AbstractPolynomialSpace<C, P>,
+        > : AbstractRationalFunctionalSpace<C, P, R> {
 
-    public val polynomialRing: AbstractPolynomialSpace<C, P>
+    public val polynomialRing: AP
 
     // region Constant-integer relation
     /**

kmath-functions/src/commonMain/kotlin/space/kscience/kmath/functions/LabeledPolynomial.kt

@@ -384,6 +384,11 @@ public class LabeledPolynomialSpace<C, A : Ring<C>>(
     // endregion
 
     // region Polynomial-integer relation
+    /**
+     * Returns sum of the polynomial and the integer represented as polynomial.
+     *
+     * The operation is equivalent to adding [other] copies of unit polynomial to [this].
+     */
     public override operator fun LabeledPolynomial<C>.plus(other: Int): LabeledPolynomial<C> =
         if (other == 0) this
         else
@@ -399,6 +404,11 @@ public class LabeledPolynomialSpace<C, A : Ring<C>>(
                         else this[degs] = result
                     }
             )
+    /**
+     * Returns difference between the polynomial and the integer represented as polynomial.
+     *
+     * The operation is equivalent to subtraction [other] copies of unit polynomial from [this].
+     */
     public override operator fun LabeledPolynomial<C>.minus(other: Int): LabeledPolynomial<C> =
         if (other == 0) this
         else
@@ -414,6 +424,11 @@ public class LabeledPolynomialSpace<C, A : Ring<C>>(
                         else this[degs] = result
                     }
             )
+    /**
+     * Returns product of the polynomial and the integer represented as polynomial.
+     *
+     * The operation is equivalent to sum of [other] copies of [this].
+     */
     public override operator fun LabeledPolynomial<C>.times(other: Int): LabeledPolynomial<C> =
         if (other == 0) zero
         else LabeledPolynomial(
@@ -425,6 +440,11 @@ public class LabeledPolynomialSpace<C, A : Ring<C>>(
     // endregion
 
     // region Integer-polynomial relation
+    /**
+     * Returns sum of the integer represented as polynomial and the polynomial.
+     *
+     * The operation is equivalent to adding [this] copies of unit polynomial to [other].
+     */
     public override operator fun Int.plus(other: LabeledPolynomial<C>): LabeledPolynomial<C> =
         if (this == 0) other
         else
@@ -440,6 +460,11 @@ public class LabeledPolynomialSpace<C, A : Ring<C>>(
                         else this[degs] = result
                     }
             )
+    /**
+     * Returns difference between the integer represented as polynomial and the polynomial.
+     *
+     * The operation is equivalent to subtraction [this] copies of unit polynomial from [other].
+     */
     public override operator fun Int.minus(other: LabeledPolynomial<C>): LabeledPolynomial<C> =
         if (this == 0) other
         else
@@ -455,6 +480,11 @@ public class LabeledPolynomialSpace<C, A : Ring<C>>(
                         else this[degs] = result
                     }
             )
+    /**
+     * Returns product of the integer represented as polynomial and the polynomial.
+     *
+     * The operation is equivalent to sum of [this] copies of [other].
+     */
     public override operator fun Int.times(other: LabeledPolynomial<C>): LabeledPolynomial<C> =
         if (this == 0) zero
         else LabeledPolynomial(
@@ -514,6 +544,9 @@ public class LabeledPolynomialSpace<C, A : Ring<C>>(
     // endregion
 
     // region Constant-polynomial relation
+    /**
+     * Returns sum of the constant represented as polynomial and the polynomial.
+     */
     override operator fun C.plus(other: LabeledPolynomial<C>): LabeledPolynomial<C> =
         if (this.isZero()) other
         else with(other.coefficients) {
@@ -530,6 +563,9 @@ public class LabeledPolynomialSpace<C, A : Ring<C>>(
                     }
             )
         }
+    /**
+     * Returns difference between the constant represented as polynomial and the polynomial.
+     */
     override operator fun C.minus(other: LabeledPolynomial<C>): LabeledPolynomial<C> =
         if (this.isZero()) other
         else with(other.coefficients) {
@@ -548,6 +584,9 @@ public class LabeledPolynomialSpace<C, A : Ring<C>>(
                     }
             )
         }
+    /**
+     * Returns product of the constant represented as polynomial and the polynomial.
+     */
     override operator fun C.times(other: LabeledPolynomial<C>): LabeledPolynomial<C> =
         if (this.isZero()) zero
         else LabeledPolynomial<C>(
@@ -560,7 +599,7 @@ public class LabeledPolynomialSpace<C, A : Ring<C>>(
 
     // region Polynomial-constant relation
     /**
-     * Returns sum of the polynomials. [other] is interpreted as [UnivariatePolynomial].
+     * Returns sum of the constant represented as polynomial and the polynomial.
      */
     override operator fun LabeledPolynomial<C>.plus(other: C): LabeledPolynomial<C> =
         if (other.isZero()) this
@@ -579,7 +618,7 @@ public class LabeledPolynomialSpace<C, A : Ring<C>>(
             )
         }
     /**
-     * Returns difference of the polynomials. [other] is interpreted as [UnivariatePolynomial].
+     * Returns difference between the constant represented as polynomial and the polynomial.
      */
     override operator fun LabeledPolynomial<C>.minus(other: C): LabeledPolynomial<C> =
         if (other.isZero()) this
@@ -600,7 +639,7 @@ public class LabeledPolynomialSpace<C, A : Ring<C>>(
             )
         }
     /**
-     * Returns product of the polynomials. [other] is interpreted as [UnivariatePolynomial].
+     * Returns product of the constant represented as polynomial and the polynomial.
      */
     override operator fun LabeledPolynomial<C>.times(other: C): LabeledPolynomial<C> =
         if (other.isZero()) zero
@@ -763,10 +802,18 @@ public class LabeledPolynomialSpace<C, A : Ring<C>>(
             )
         }
 
+    /**
+     * Instance of zero polynomial (zero of the polynomial ring).
+     */
     override val zero: LabeledPolynomial<C> = LabeledPolynomial<C>(mapOf(emptyMap<Variable, UInt>() to constantZero))
+    /**
+     * Instance of unit polynomial (unit of the polynomial ring).
+     */
     override val one: LabeledPolynomial<C> = LabeledPolynomial<C>(mapOf(emptyMap<Variable, UInt>() to constantOne))
 
-    // TODO: Docs
+    /**
+     * Checks equality of the polynomials.
+     */
     override infix fun LabeledPolynomial<C>.equalsTo(other: LabeledPolynomial<C>): Boolean =
         when {
             this === other -> true
@@ -832,7 +879,10 @@ public class LabeledPolynomialSpace<C, A : Ring<C>>(
             }
             foundAbsoluteTermAndItIsNotZero
         }
-
+    /**
+     * If polynomial is a constant polynomial represents and returns it as constant.
+     * Otherwise, (when the polynomial is not constant polynomial) returns `null`.
+     */
     override fun LabeledPolynomial<C>.asConstantOrNull(): C? =
         with(coefficients) {
             if(isConstant()) getOrElse(emptyMap()) { constantZero }

kmath-functions/src/commonMain/kotlin/space/kscience/kmath/functions/LabeledRationalFunction.kt

@@ -85,7 +85,12 @@ internal fun labeledRationalFunctionError(message: Any): Nothing = throw Labeled
 
 public class LabeledRationalFunctionSpace<C, A: Ring<C>>(
     public val ring: A,
-) : AbstractRationalFunctionalSpaceOverPolynomialSpace<C, LabeledPolynomial<C>, LabeledRationalFunction<C>, A> {
+) : AbstractRationalFunctionalSpaceOverPolynomialSpace<
+        C,
+        LabeledPolynomial<C>,
+        LabeledRationalFunction<C>,
+        LabeledPolynomialSpace<C, A>,
+        > {
 
     override val polynomialRing : LabeledPolynomialSpace<C, A> = LabeledPolynomialSpace(ring)
 

kmath-functions/src/commonMain/kotlin/space/kscience/kmath/functions/NumberedPolynomial.kt

@@ -267,6 +267,11 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
     public final override val ring: A,
 ) : AbstractPolynomialSpaceOverRing<C, NumberedPolynomial<C>, A> {
     // region Polynomial-integer relation
+    /**
+     * Returns sum of the polynomial and the integer represented as polynomial.
+     *
+     * The operation is equivalent to adding [other] copies of unit polynomial to [this].
+     */
     public override operator fun NumberedPolynomial<C>.plus(other: Int): NumberedPolynomial<C> =
         if (other == 0) this
         else
@@ -282,6 +287,11 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
                         else this[degs] = result
                     }
             )
+    /**
+     * Returns difference between the polynomial and the integer represented as polynomial.
+     *
+     * The operation is equivalent to subtraction [other] copies of unit polynomial from [this].
+     */
     public override operator fun NumberedPolynomial<C>.minus(other: Int): NumberedPolynomial<C> =
         if (other == 0) this
         else
@@ -297,6 +307,11 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
                         else this[degs] = result
                     }
             )
+    /**
+     * Returns product of the polynomial and the integer represented as polynomial.
+     *
+     * The operation is equivalent to sum of [other] copies of [this].
+     */
     public override operator fun NumberedPolynomial<C>.times(other: Int): NumberedPolynomial<C> =
         if (other == 0) zero
         else NumberedPolynomial(
@@ -308,6 +323,11 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
     // endregion
 
     // region Integer-polynomial relation
+    /**
+     * Returns sum of the integer represented as polynomial and the polynomial.
+     *
+     * The operation is equivalent to adding [this] copies of unit polynomial to [other].
+     */
     public override operator fun Int.plus(other: NumberedPolynomial<C>): NumberedPolynomial<C> =
         if (this == 0) other
         else
@@ -323,6 +343,11 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
                         else this[degs] = result
                     }
             )
+    /**
+     * Returns difference between the integer represented as polynomial and the polynomial.
+     *
+     * The operation is equivalent to subtraction [this] copies of unit polynomial from [other].
+     */
     public override operator fun Int.minus(other: NumberedPolynomial<C>): NumberedPolynomial<C> =
         if (this == 0) other
         else
@@ -338,6 +363,11 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
                         else this[degs] = result
                     }
             )
+    /**
+     * Returns product of the integer represented as polynomial and the polynomial.
+     *
+     * The operation is equivalent to sum of [this] copies of [other].
+     */
     public override operator fun Int.times(other: NumberedPolynomial<C>): NumberedPolynomial<C> =
         if (this == 0) zero
         else NumberedPolynomial(
@@ -349,6 +379,9 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
     // endregion
 
     // region Constant-polynomial relation
+    /**
+     * Returns sum of the constant represented as polynomial and the polynomial.
+     */
     override operator fun C.plus(other: NumberedPolynomial<C>): NumberedPolynomial<C> =
         if (this.isZero()) other
         else with(other.coefficients) {
@@ -365,6 +398,9 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
                     }
             )
         }
+    /**
+     * Returns difference between the constant represented as polynomial and the polynomial.
+     */
     override operator fun C.minus(other: NumberedPolynomial<C>): NumberedPolynomial<C> =
         if (this.isZero()) -other
         else with(other.coefficients) {
@@ -383,6 +419,9 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
                     }
             )
         }
+    /**
+     * Returns product of the constant represented as polynomial and the polynomial.
+     */
     override operator fun C.times(other: NumberedPolynomial<C>): NumberedPolynomial<C> =
         if (this.isZero()) zero
         else NumberedPolynomial<C>(
@@ -395,7 +434,7 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
 
     // region Polynomial-constant relation
     /**
-     * Returns sum of the polynomials. [other] is interpreted as [NumberedPolynomial].
+     * Returns sum of the constant represented as polynomial and the polynomial.
      */
     override operator fun NumberedPolynomial<C>.plus(other: C): NumberedPolynomial<C> =
         if (other.isZero()) this
@@ -414,7 +453,7 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
             )
         }
     /**
-     * Returns difference of the polynomials. [other] is interpreted as [NumberedPolynomial].
+     * Returns difference between the constant represented as polynomial and the polynomial.
      */
     override operator fun NumberedPolynomial<C>.minus(other: C): NumberedPolynomial<C> =
         if (other.isZero()) this
@@ -433,7 +472,7 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
             )
         }
     /**
-     * Returns product of the polynomials. [other] is interpreted as [NumberedPolynomial].
+     * Returns product of the constant represented as polynomial and the polynomial.
      */
     override operator fun NumberedPolynomial<C>.times(other: C): NumberedPolynomial<C> =
         if (other.isZero()) zero
@@ -496,7 +535,13 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
                 )
         }
 
+    /**
+     * Check if the instant is zero polynomial.
+     */
     public override fun NumberedPolynomial<C>.isZero(): Boolean = coefficients.values.all { it.isZero() }
+    /**
+     * Check if the instant is unit polynomial.
+     */
     public override fun NumberedPolynomial<C>.isOne(): Boolean =
         with(coefficients) {
             var foundAbsoluteTermAndItIsOne = false
@@ -509,6 +554,9 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
             }
             foundAbsoluteTermAndItIsOne
         }
+    /**
+     * Check if the instant is minus unit polynomial.
+     */
     public override fun NumberedPolynomial<C>.isMinusOne(): Boolean =
         with(coefficients) {
             var foundAbsoluteTermAndItIsMinusOne = false
@@ -522,7 +570,13 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
             foundAbsoluteTermAndItIsMinusOne
         }
 
+    /**
+     * Instance of zero polynomial (zero of the polynomial ring).
+     */
     override val zero: NumberedPolynomial<C> = NumberedPolynomial<C>(emptyMap())
+    /**
+     * Instance of unit polynomial (unit of the polynomial ring).
+     */
     override val one: NumberedPolynomial<C> =
         NumberedPolynomial<C>(
             mapOf(
@@ -530,7 +584,9 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
             )
         )
 
-    // TODO: Docs
+    /**
+     * Checks equality of the polynomials.
+     */
     override infix fun NumberedPolynomial<C>.equalsTo(other: NumberedPolynomial<C>): Boolean =
         when {
             this === other -> true
@@ -591,7 +647,10 @@ public open class NumberedPolynomialSpace<C, A : Ring<C>>(
             }
             foundAbsoluteTermAndItIsNotZero
         }
-
+    /**
+     * If polynomial is a constant polynomial represents and returns it as constant.
+     * Otherwise, (when the polynomial is not constant polynomial) returns `null`.
+     */
     override fun NumberedPolynomial<C>.asConstantOrNull(): C? =
         with(coefficients) {
             if(isConstant()) getOrElse(emptyList()) { constantZero }

kmath-functions/src/commonMain/kotlin/space/kscience/kmath/functions/NumberedRationalFunction.kt

@@ -82,7 +82,12 @@ internal fun numberedRationalFunctionError(message: Any): Nothing = throw Number
 
 public class NumberedRationalFunctionSpace<C, A: Ring<C>> (
     public val ring: A,
-) : AbstractRationalFunctionalSpaceOverPolynomialSpace<C, NumberedPolynomial<C>, NumberedRationalFunction<C>, A> {
+) : AbstractRationalFunctionalSpaceOverPolynomialSpace<
+        C,
+        NumberedPolynomial<C>,
+        NumberedRationalFunction<C>,
+        NumberedPolynomialSpace<C, A>,
+        > {
 
     override val polynomialRing : NumberedPolynomialSpace<C, A> = NumberedPolynomialSpace(ring)
 

kmath-functions/src/commonMain/kotlin/space/kscience/kmath/functions/Polynomial.kt

@@ -68,10 +68,15 @@ public fun <T> T.asPolynomial() : Polynomial<T> = Polynomial(listOf(this))
  */
 //@Suppress("INAPPLICABLE_JVM_NAME") // TODO: KT-31420
 public open class PolynomialSpace<C, A : Ring<C>>(
-    public final override val ring: A,
+    public override val ring: A,
 ) : AbstractPolynomialSpaceOverRing<C, Polynomial<C>, A> {
 
     // region Polynomial-integer relation
+    /**
+     * Returns sum of the polynomial and the integer represented as polynomial.
+     *
+     * The operation is equivalent to adding [other] copies of unit polynomial to [this].
+     */
     public override operator fun Polynomial<C>.plus(other: Int): Polynomial<C> =
         if (other == 0) this
         else
@@ -89,6 +94,11 @@ public open class PolynomialSpace<C, A : Ring<C>>(
                         }
                     }
             )
+    /**
+     * Returns difference between the polynomial and the integer represented as polynomial.
+     *
+     * The operation is equivalent to subtraction [other] copies of unit polynomial from [this].
+     */
     public override operator fun Polynomial<C>.minus(other: Int): Polynomial<C> =
         if (other == 0) this
         else
@@ -106,6 +116,11 @@ public open class PolynomialSpace<C, A : Ring<C>>(
                         }
                     }
             )
+    /**
+     * Returns product of the polynomial and the integer represented as polynomial.
+     *
+     * The operation is equivalent to sum of [other] copies of [this].
+     */
     public override operator fun Polynomial<C>.times(other: Int): Polynomial<C> =
         if (other == 0) zero
         else Polynomial(
@@ -116,6 +131,11 @@ public open class PolynomialSpace<C, A : Ring<C>>(
     // endregion
 
     // region Integer-polynomial relation
+    /**
+     * Returns sum of the integer represented as polynomial and the polynomial.
+     *
+     * The operation is equivalent to adding [this] copies of unit polynomial to [other].
+     */
     public override operator fun Int.plus(other: Polynomial<C>): Polynomial<C> =
         if (this == 0) other
         else
@@ -133,6 +153,11 @@ public open class PolynomialSpace<C, A : Ring<C>>(
                         }
                     }
             )
+    /**
+     * Returns difference between the integer represented as polynomial and the polynomial.
+     *
+     * The operation is equivalent to subtraction [this] copies of unit polynomial from [other].
+     */
     public override operator fun Int.minus(other: Polynomial<C>): Polynomial<C> =
         if (this == 0) other
         else
@@ -152,6 +177,11 @@ public open class PolynomialSpace<C, A : Ring<C>>(
                         }
                     }
             )
+    /**
+     * Returns product of the integer represented as polynomial and the polynomial.
+     *
+     * The operation is equivalent to sum of [this] copies of [other].
+     */
     public override operator fun Int.times(other: Polynomial<C>): Polynomial<C> =
         if (this == 0) zero
         else Polynomial(
@@ -162,6 +192,9 @@ public open class PolynomialSpace<C, A : Ring<C>>(
     // endregion
 
     // region Constant-polynomial relation
+    /**
+     * Returns sum of the constant represented as polynomial and the polynomial.
+     */
     public override operator fun C.plus(other: Polynomial<C>): Polynomial<C> =
         if (this.isZero()) other
         else with(other.coefficients) {
@@ -180,9 +213,9 @@ public open class PolynomialSpace<C, A : Ring<C>>(
                     }
             )
         }
-//        if (degree == -1) UnivariatePolynomial(other) else UnivariatePolynomial(
+    /**
-//            listOf(coefficients[0] + other) + coefficients.subList(1, degree + 1)
+     * Returns difference between the constant represented as polynomial and the polynomial.
-//        )
+     */
     public override operator fun C.minus(other: Polynomial<C>): Polynomial<C> =
         if (this.isZero()) other
         else with(other.coefficients) {
@@ -203,9 +236,9 @@ public open class PolynomialSpace<C, A : Ring<C>>(
                     }
             )
         }
-//        if (degree == -1) UnivariatePolynomial(other) else UnivariatePolynomial(
+    /**
-//            listOf(coefficients[0] + other) + coefficients.subList(1, degree + 1)
+     * Returns product of the constant represented as polynomial and the polynomial.
-//        )
+     */
     public override operator fun C.times(other: Polynomial<C>): Polynomial<C> =
         if (this.isZero()) other
         else Polynomial(
@@ -216,6 +249,9 @@ public open class PolynomialSpace<C, A : Ring<C>>(
     // endregion
 
     // region Polynomial-constant relation
+    /**
+     * Returns sum of the constant represented as polynomial and the polynomial.
+     */
     public override operator fun Polynomial<C>.plus(other: C): Polynomial<C> =
         if (other.isZero()) this
         else with(coefficients) {
@@ -234,9 +270,9 @@ public open class PolynomialSpace<C, A : Ring<C>>(
                     }
             )
         }
-//        if (degree == -1) UnivariatePolynomial(other) else UnivariatePolynomial(
+    /**
-//            listOf(coefficients[0] + other) + coefficients.subList(1, degree + 1)
+     * Returns difference between the constant represented as polynomial and the polynomial.
-//        )
+     */
     public override operator fun Polynomial<C>.minus(other: C): Polynomial<C> =
         if (other.isZero()) this
         else with(coefficients) {
@@ -255,9 +291,9 @@ public open class PolynomialSpace<C, A : Ring<C>>(
                     }
             )
         }
-//        if (degree == -1) UnivariatePolynomial(-other) else UnivariatePolynomial(
+    /**
-//            listOf(coefficients[0] - other) + coefficients.subList(1, degree + 1)
+     * Returns product of the constant represented as polynomial and the polynomial.
-//        )
+     */
     public override operator fun Polynomial<C>.times(other: C): Polynomial<C> =
         if (other.isZero()) this
         else Polynomial(
@@ -268,8 +304,14 @@ public open class PolynomialSpace<C, A : Ring<C>>(
     // endregion
 
     // region Polynomial-polynomial relation
+    /**
+     * Returns negation of the polynomial.
+     */
     public override operator fun Polynomial<C>.unaryMinus(): Polynomial<C> =
         Polynomial(coefficients.map { -it })
+    /**
+     * Returns sum of the polynomials.
+     */
     public override operator fun Polynomial<C>.plus(other: Polynomial<C>): Polynomial<C> =
         Polynomial(
             (0..max(degree, other.degree))
@@ -282,6 +324,9 @@ public open class PolynomialSpace<C, A : Ring<C>>(
                 }
                 .ifEmpty { listOf(constantZero) }
         )
+    /**
+     * Returns difference of the polynomials.
+     */
     public override operator fun Polynomial<C>.minus(other: Polynomial<C>): Polynomial<C> =
         Polynomial(
             (0..max(degree, other.degree))
@@ -294,6 +339,9 @@ public open class PolynomialSpace<C, A : Ring<C>>(
                 }
                 .ifEmpty { listOf(constantZero) }
         )
+    /**
+     * Returns product of the polynomials.
+     */
     public override operator fun Polynomial<C>.times(other: Polynomial<C>): Polynomial<C> {
         val thisDegree = degree
         val otherDegree = other.degree
@@ -313,15 +361,39 @@ public open class PolynomialSpace<C, A : Ring<C>>(
         }
     }
 
+    /**
+     * Check if the instant is zero polynomial.
+     */
     public override fun Polynomial<C>.isZero(): Boolean = coefficients.all { it.isZero() }
+    /**
+     * Check if the instant is unit polynomial.
+     */
     public override fun Polynomial<C>.isOne(): Boolean =
-        with(coefficients) { isNotEmpty() && asSequence().withIndex().any { (index, c) -> if (index == 0) c.isOne() else c.isZero() } } // TODO: It's better to write new methods like `anyIndexed`. But what's better way to do it?
+        with(coefficients) {
+            isNotEmpty() &&
+                    asSequence().withIndex().any { (index, c) -> if (index == 0) c.isOne() else c.isZero() } // TODO: It's better to write new methods like `anyIndexed`. But what's better way to do it?
+        }
+    /**
+     * Check if the instant is minus unit polynomial.
+     */
     public override fun Polynomial<C>.isMinusOne(): Boolean =
-        with(coefficients) { isNotEmpty() && asSequence().withIndex().any { (index, c) -> if (index == 0) c.isMinusOne() else c.isZero() } } // TODO: It's better to write new methods like `anyIndexed`. But what's better way to do it?
+        with(coefficients) {
+            isNotEmpty() &&
+                    asSequence().withIndex().any { (index, c) -> if (index == 0) c.isMinusOne() else c.isZero() } // TODO: It's better to write new methods like `anyIndexed`. But what's better way to do it?
+        }
 
+    /**
+     * Instance of zero polynomial (zero of the polynomial ring).
+     */
     override val zero: Polynomial<C> = Polynomial(emptyList())
+    /**
+     * Instance of unit constant (unit of the underlying ring).
+     */
     override val one: Polynomial<C> = Polynomial(listOf(constantZero))
 
+    /**
+     * Checks equality of the polynomials.
+     */
     public override infix fun Polynomial<C>.equalsTo(other: Polynomial<C>): Boolean =
         when {
             this === other -> true
@@ -334,9 +406,16 @@ public open class PolynomialSpace<C, A : Ring<C>>(
     // endregion
 
     // region Polynomial properties
-
+    /**
+     * Degree of the polynomial, [see also](https://en.wikipedia.org/wiki/Degree_of_a_polynomial). If the polynomial is
+     * zero, degree is -1.
+     */
     public override val Polynomial<C>.degree: Int get() = coefficients.indexOfLast { it != constantZero }
 
+    /**
+     * If polynomial is a constant polynomial represents and returns it as constant.
+     * Otherwise, (when the polynomial is not constant polynomial) returns `null`.
+     */
     public override fun Polynomial<C>.asConstantOrNull(): C? =
         with(coefficients) {
             when {
@@ -345,7 +424,6 @@ public open class PolynomialSpace<C, A : Ring<C>>(
                 else -> first()
             }
         }
-    public override fun Polynomial<C>.asConstant(): C = asConstantOrNull() ?: error("Can not represent non-constant polynomial as a constant")
 
     @Suppress("NOTHING_TO_INLINE")
     public inline fun Polynomial<C>.substitute(argument: C): C = this.substitute(ring, argument)

kmath-functions/src/commonMain/kotlin/space/kscience/kmath/functions/RationalFunction.kt

@@ -67,7 +67,12 @@ internal fun rationalFunctionError(message: Any): Nothing = throw RationalFuncti
 
 public class RationalFunctionSpace<C, A : Ring<C>> (
     public val ring: A,
-) : AbstractRationalFunctionalSpaceOverPolynomialSpace<C, Polynomial<C>, RationalFunction<C>, A> {
+) : AbstractRationalFunctionalSpaceOverPolynomialSpace<
+        C,
+        Polynomial<C>,
+        RationalFunction<C>,
+        PolynomialSpace<C, A>,
+        > {
 
     override val polynomialRing : PolynomialSpace<C, A> = PolynomialSpace(ring)