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

@@ -262,12 +262,14 @@ public fun <C> NumberedRationalFunction<C>.substitute(ring: Ring<C>, args: Buffe
         numerator.substitute(ring, args) / denominator.substitute(ring, args)
     }
 
+internal const val fullSubstitutionExceptionMessage: String = "Fully substituting buffer should cover all variables of the polynomial."
+
 /**
  * Substitutes provided Double arguments [args] into [this] Double polynomial.
  */
 public fun NumberedPolynomial<Double>.substituteFully(args: Buffer<Double>): Double = Double.algebra {
     val lastSubstitutionVariable = args.size - 1
-    require(coefficients.keys.all { it.lastIndex <= lastSubstitutionVariable }) { "Fully substituting buffer should cover all variables of the polynomial." }
+    require(coefficients.keys.all { it.lastIndex <= lastSubstitutionVariable }) { fullSubstitutionExceptionMessage }
     coefficients.entries.fold(.0) { acc, (degs, c) ->
         acc + degs.foldIndexed(c) { variable, product, deg ->
             if (deg == 0u) product else product * args[variable].pow(deg.toInt())
@@ -280,7 +282,7 @@ public fun NumberedPolynomial<Double>.substituteFully(args: Buffer<Double>): Dou
  */
 public fun <C> NumberedPolynomial<C>.substituteFully(ring: Ring<C>, args: Buffer<C>): C = ring {
     val lastSubstitutionVariable = args.size - 1
-    require(coefficients.keys.all { it.lastIndex <= lastSubstitutionVariable }) { "Fully substituting buffer should cover all variables of the polynomial." }
+    require(coefficients.keys.all { it.lastIndex <= lastSubstitutionVariable }) { fullSubstitutionExceptionMessage }
     coefficients.entries.fold(zero) { acc, (degs, c) ->
         acc + degs.foldIndexed(c) { variable, product, deg ->
             if (deg == 0u) product else product * power(args[variable], deg)

kmath-functions/src/commonTest/kotlin/space/kscience/kmath/test/misc/assertion.kt

@@ -8,6 +8,7 @@ package space.kscience.kmath.test.misc
 import space.kscience.kmath.functions.NumberedPolynomial
 import space.kscience.kmath.functions.NumberedRationalFunction
 import kotlin.test.assertEquals
+import kotlin.test.assertFailsWith
 
 
 fun <T> assertContentEquals(expected: Map<T, Double>, actual: Map<T, Double>, absoluteTolerance: Double, message: String? = null) {
@@ -45,4 +46,15 @@ fun assertEquals(
         absoluteTolerance,
         message
     )
-}
+}
+
+inline fun <reified T : Throwable> assertFailsWithTypeAndMessage(
+    expectedMessage: String? = null,
+    assertionMessage: String? = null,
+    block: () -> Unit
+) =
+    assertEquals(
+        expectedMessage,
+        assertFailsWith(T::class, assertionMessage, block).message,
+        assertionMessage
+    )