Fix part of #4044: Add support for expression evaluation & conversion to LaTeX

scripts/assets/file_content_validation_checks.textproto

@@ -289,5 +289,6 @@ file_content_checks {
   exempted_file_name: "scripts/src/javatests/org/oppia/android/scripts/regex/RegexPatternValidationCheckTest.kt"
   exempted_file_name: "utility/src/test/java/org/oppia/android/util/math/MathExpressionParserTest.kt"
   exempted_file_name: "utility/src/test/java/org/oppia/android/util/math/MathTokenizerTest.kt"
+  exempted_file_name: "utility/src/test/java/org/oppia/android/util/math/RealExtensionsTest.kt"
   exempted_file_patterns: "testing/src/main/java/org/oppia/android/testing/junit/.+?\\.kt"
 }

testing/src/main/java/org/oppia/android/testing/math/MathEquationSubject.kt

@@ -1,12 +1,14 @@
 package org.oppia.android.testing.math
 
 import com.google.common.truth.FailureMetadata
+import com.google.common.truth.StringSubject
 import com.google.common.truth.Truth.assertAbout
 import com.google.common.truth.Truth.assertThat
 import com.google.common.truth.extensions.proto.LiteProtoSubject
 import org.oppia.android.app.model.MathEquation
 import org.oppia.android.testing.math.MathEquationSubject.Companion.assertThat
 import org.oppia.android.testing.math.MathExpressionSubject.Companion.assertThat
+import org.oppia.android.util.math.toRawLatex
 
 // TODO(#4097): Add tests for this class.
 
@@ -34,6 +36,26 @@ class MathEquationSubject private constructor(
    */
   fun hasRightHandSideThat(): MathExpressionSubject = assertThat(actual.rightSide)
 
+  /**
+   * Returns a [StringSubject] to verify the LaTeX conversion of the tested [MathEquation].
+   *
+   * For more details on LaTeX conversion, see [toRawLatex]. Note that this method, in contrast to
+   * [convertsWithFractionsToLatexStringThat], retains division operations as-is.
+   */
+  fun convertsToLatexStringThat(): StringSubject =
+    assertThat(convertToLatex(divAsFraction = false))
+
+  /**
+   * Returns a [StringSubject] to verify the LaTeX conversion of the tested [MathEquation].
+   *
+   * For more details on LaTeX conversion, see [toRawLatex]. Note that this method, in contrast to
+   * [convertsToLatexStringThat], treats divisions as fractions.
+   */
+  fun convertsWithFractionsToLatexStringThat(): StringSubject =
+    assertThat(convertToLatex(divAsFraction = true))
+
+  private fun convertToLatex(divAsFraction: Boolean): String = actual.toRawLatex(divAsFraction)
+
   companion object {
     /**
      * Returns a new [MathEquationSubject] to verify aspects of the specified [MathEquation] value.

testing/src/main/java/org/oppia/android/testing/math/MathExpressionSubject.kt

@@ -1,6 +1,8 @@
 package org.oppia.android.testing.math
 
+import com.google.common.truth.DoubleSubject
 import com.google.common.truth.FailureMetadata
+import com.google.common.truth.IntegerSubject
 import com.google.common.truth.StringSubject
 import com.google.common.truth.Truth.assertAbout
 import com.google.common.truth.Truth.assertThat
@@ -18,6 +20,8 @@ import org.oppia.android.app.model.MathUnaryOperation
 import org.oppia.android.app.model.Real
 import org.oppia.android.testing.math.MathExpressionSubject.Companion.assertThat
 import org.oppia.android.testing.math.RealSubject.Companion.assertThat
+import org.oppia.android.util.math.evaluateAsNumericExpression
+import org.oppia.android.util.math.toRawLatex
 
 // TODO(#4097): Add tests for this class.
 
@@ -91,6 +95,65 @@ class MathExpressionSubject private constructor(
     ExpressionComparator.createFromExpression(actual).also(init)
   }
 
+  /**
+   * Assumes that this expression evaluates to a fraction (i.e. [Real.getRational]) and returns a
+   * [FractionSubject] to verify the computed value.
+   *
+   * Note that this should only be used for numeric expressions as variable expressions cannot be
+   * evaluated. For more context on expression evaluation, see [evaluateAsNumericExpression].
+   */
+  fun evaluatesToRationalThat(): FractionSubject =
+    FractionSubject.assertThat(evaluateAsReal(expectedType = Real.RealTypeCase.RATIONAL).rational)
+
+  /**
+   * Assumes that this expression evaluates to an irrational (i.e. [Real.getIrrational]) and returns
+   * a [DoubleSubject] to verify the computed value.
+   *
+   * Note that this should only be used for numeric expressions as variable expressions cannot be
+   * evaluated. For more context on expression evaluation, see [evaluateAsNumericExpression].
+   */
+  fun evaluatesToIrrationalThat(): DoubleSubject =
+    assertThat(evaluateAsReal(expectedType = Real.RealTypeCase.IRRATIONAL).irrational)
+
+  /**
+   * Assumes that this expression evaluates to an integer (i.e. [Real.getInteger]) and returns an
+   * [IntegerSubject] to verify the computed value.
+   *
+   * Note that this should only be used for numeric expressions as variable expressions cannot be
+   * evaluated. For more context on expression evaluation, see [evaluateAsNumericExpression].
+   */
+  fun evaluatesToIntegerThat(): IntegerSubject =
+    assertThat(evaluateAsReal(expectedType = Real.RealTypeCase.INTEGER).integer)
+
+  /**
+   * Returns a [StringSubject] to verify the LaTeX conversion of the tested [MathExpression].
+   *
+   * For more details on LaTeX conversion, see [toRawLatex]. Note that this method, in contrast to
+   * [convertsWithFractionsToLatexStringThat], retains division operations as-is.
+   */
+  fun convertsToLatexStringThat(): StringSubject =
+    assertThat(convertToLatex(divAsFraction = false))
+
+  /**
+   * Returns a [StringSubject] to verify the LaTeX conversion of the tested [MathExpression].
+   *
+   * For more details on LaTeX conversion, see [toRawLatex]. Note that this method, in contrast to
+   * [convertsToLatexStringThat], treats divisions as fractions.
+   */
+  fun convertsWithFractionsToLatexStringThat(): StringSubject =
+    assertThat(convertToLatex(divAsFraction = true))
+
+  private fun evaluateAsReal(expectedType: Real.RealTypeCase): Real {
+    val real = actual.evaluateAsNumericExpression()
+    assertWithMessage("Failed to evaluate numeric expression").that(real).isNotNull()
+    assertWithMessage("Expected constant to evaluate to $expectedType")
+      .that(real?.realTypeCase)
+      .isEqualTo(expectedType)
+    return checkNotNull(real) // Just to remove the nullable operator; the actual check is above.
+  }
+
+  private fun convertToLatex(divAsFraction: Boolean): String = actual.toRawLatex(divAsFraction)
+
   /**
    * DSL syntax provider for verifying the structure of a [MathExpression].
    *

testing/src/main/java/org/oppia/android/testing/math/RealSubject.kt

@@ -22,15 +22,17 @@ import org.oppia.android.testing.math.FractionSubject.Companion.assertThat
  */
 class RealSubject private constructor(
   metadata: FailureMetadata,
-  private val actual: Real
+  private val actual: Real?
 ) : LiteProtoSubject(metadata, actual) {
+  private val nonNullActual by lazy { checkNotNull(actual) { "Expected real to be non-null" } }
+
   /**
    * Returns a [FractionSubject] to test [Real.getRational]. This will fail if the [Real] pertaining
    * to this subject is not of type rational.
    */
   fun isRationalThat(): FractionSubject {
     verifyTypeToBe(Real.RealTypeCase.RATIONAL)
-    return assertThat(actual.rational)
+    return assertThat(nonNullActual.rational)
   }
 
   /**
@@ -39,7 +41,7 @@ class RealSubject private constructor(
    */
   fun isIrrationalThat(): DoubleSubject {
     verifyTypeToBe(Real.RealTypeCase.IRRATIONAL)
-    return assertThat(actual.irrational)
+    return assertThat(nonNullActual.irrational)
   }
 
   /**
@@ -48,17 +50,17 @@ class RealSubject private constructor(
    */
   fun isIntegerThat(): IntegerSubject {
     verifyTypeToBe(Real.RealTypeCase.INTEGER)
-    return assertThat(actual.integer)
+    return assertThat(nonNullActual.integer)
   }
 
   private fun verifyTypeToBe(expected: Real.RealTypeCase) {
-    assertWithMessage("Expected real type to be $expected, not: ${actual.realTypeCase}")
-      .that(actual.realTypeCase)
+    assertWithMessage("Expected real type to be $expected, not: ${nonNullActual.realTypeCase}")
+      .that(nonNullActual.realTypeCase)
       .isEqualTo(expected)
   }
 
   companion object {
     /** Returns a new [RealSubject] to verify aspects of the specified [Real] value. */
-    fun assertThat(actual: Real): RealSubject = assertAbout(::RealSubject).that(actual)
+    fun assertThat(actual: Real?): RealSubject = assertAbout(::RealSubject).that(actual)
   }
 }

utility/src/main/java/org/oppia/android/util/math/BUILD.bazel

@@ -4,20 +4,18 @@ General-purpose mathematics utilities, especially for supporting math-based inte
 
 load("@io_bazel_rules_kotlin//kotlin:kotlin.bzl", "kt_android_library")
 
-kt_android_library(
+android_library(
     name = "extensions",
-    srcs = [
-        "FloatExtensions.kt",
-        "FractionExtensions.kt",
-        "PolynomialExtensions.kt",
-        "RatioExtensions.kt",
-        "RealExtensions.kt",
-    ],
     visibility = [
         "//:oppia_api_visibility",
     ],
-    deps = [
-        "//model/src/main/proto:math_java_proto_lite",
+    exports = [
+        ":float_extensions",
+        ":fraction_extensions",
+        ":math_expression_extensions",
+        ":polynomial_extensions",
+        ":ratio_extensions",
+        ":real_extensions",
     ],
 )
 
@@ -39,12 +37,12 @@ kt_android_library(
         "MathExpressionParser.kt",
     ],
     visibility = [
-        "//:oppia_testing_visibility",
+        "//:oppia_api_visibility",
     ],
     deps = [
-        ":extensions",
         ":math_parsing_error",
         ":peekable_iterator",
+        ":real_extensions",
         ":tokenizer",
         "//model/src/main/proto:math_java_proto_lite",
     ],
@@ -86,3 +84,94 @@ kt_android_library(
         "//:oppia_testing_visibility",
     ],
 )
+
+kt_android_library(
+    name = "float_extensions",
+    srcs = [
+        "FloatExtensions.kt",
+    ],
+    deps = [
+        "//model/src/main/proto:math_java_proto_lite",
+    ],
+)
+
+kt_android_library(
+    name = "fraction_extensions",
+    srcs = [
+        "FractionExtensions.kt",
+    ],
+    deps = [
+        "//model/src/main/proto:math_java_proto_lite",
+    ],
+)
+
+kt_android_library(
+    name = "math_expression_extensions",
+    srcs = [
+        "MathExpressionExtensions.kt",
+    ],
+    deps = [
+        ":expression_to_latex_converter",
+        ":numeric_expression_evaluator",
+        "//model/src/main/proto:math_java_proto_lite",
+    ],
+)
+
+kt_android_library(
+    name = "polynomial_extensions",
+    srcs = [
+        "PolynomialExtensions.kt",
+    ],
+    deps = [
+        ":real_extensions",
+        "//model/src/main/proto:math_java_proto_lite",
+    ],
+)
+
+kt_android_library(
+    name = "ratio_extensions",
+    srcs = [
+        "RatioExtensions.kt",
+    ],
+    deps = [
+        ":fraction_extensions",
+        "//model/src/main/proto:math_java_proto_lite",
+    ],
+)
+
+kt_android_library(
+    name = "real_extensions",
+    srcs = [
+        "RealExtensions.kt",
+    ],
+    deps = [
+        ":float_extensions",
+        ":fraction_extensions",
+        "//model/src/main/proto:math_java_proto_lite",
+    ],
+)
+
+kt_android_library(
+    name = "expression_to_latex_converter",
+    srcs = [
+        "ExpressionToLatexConverter.kt",
+    ],
+    visibility = [
+        "//:oppia_testing_visibility",
+    ],
+    deps = [
+        ":real_extensions",
+        "//model/src/main/proto:math_java_proto_lite",
+    ],
+)
+
+kt_android_library(
+    name = "numeric_expression_evaluator",
+    srcs = [
+        "NumericExpressionEvaluator.kt",
+    ],
+    deps = [
+        ":real_extensions",
+        "//model/src/main/proto:math_java_proto_lite",
+    ],
+)