Initial commit.

Simple string calculator based on Clean Architecture.

Layers:
*CORE >>> calculating string expression
*UI >>> user input handling, calculation result handling

Features:
*simple arithmetic operations (addition, subtraction, multiplication, division)
*unary subtraction
*operation's priority assignment

.gitignore

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+*.iml
+.gradle
+/local.properties
+/.idea/caches
+/.idea/libraries
+/.idea/modules.xml
+/.idea/workspace.xml
+/.idea/navEditor.xml
+/.idea/assetWizardSettings.xml
+.DS_Store
+/build
+/captures
+.externalNativeBuild

app/.gitignore

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+/build

app/build.gradle

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+apply plugin: 'com.android.application'
+
+android {
+    compileSdkVersion 28
+    buildToolsVersion '28.0.3'
+    defaultConfig {
+        applicationId "ru.neurospb.app_icon"
+        minSdkVersion 15
+        targetSdkVersion 28
+        versionCode 1
+        versionName "1.0"
+        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+    }
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+        }
+    }
+}
+
+dependencies {
+    implementation fileTree(dir: 'libs', include: ['*.jar'])
+    implementation 'com.android.support:appcompat-v7:28.0.0'
+    testImplementation 'junit:junit:4.12'
+    androidTestImplementation 'com.android.support.test:runner:1.0.2'
+    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
+    //V7 support libs
+    implementation 'com.android.support:appcompat-v7:28.0.0'
+    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
+    //material design support lib
+    implementation 'com.android.support:design:28.0.0'
+}

app/src/main/AndroidManifest.xml

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+<manifest
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    package="ru.neurospb.calculator">
+
+    <application
+        android:allowBackup="false"
+        android:icon="@mipmap/app_icon"
+        android:label="@string/app_name"
+        android:supportsRtl="true"
+        android:theme="@style/AppTheme"
+        tools:ignore="GoogleAppIndexingWarning">
+
+        <activity
+            android:name=".ui.views.base.StartPointActivity"
+            android:launchMode="singleInstance">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+
+    </application>
+</manifest>

app/src/main/java/ru/neurospb/calculator/core/gateways/IUIResultHandler.java

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+package ru.neurospb.calculator.core.gateways;
+
+/**
+ * GATEWAY for UI layer
+ * Функционал для получателя(обработчика) результата выполнения действий системы (use case)
+ *
+ * @author Алексей Утовка
+ * @version а1
+ */
+
+public interface IUIResultHandler {
+    //обратный вызов для передачи результата Действия в слой UI
+    void onResult(String result);
+}

app/src/main/java/ru/neurospb/calculator/core/models/IMathUnit.java

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+package ru.neurospb.calculator.core.models;
+
+/**
+ * Базовый функционал для математических единиц.
+ *
+ * @author Алексей Утовка
+ * @version а1
+ */
+
+public interface IMathUnit {
+    //возвращает тип математической единицы
+    int getType();
+}

app/src/main/java/ru/neurospb/calculator/core/models/Number.java

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+package ru.neurospb.calculator.core.models;
+
+/**
+ * Model.
+ * Модель числа
+ *
+ * @author Алексей Утовка
+ * @version а1
+ */
+
+public class Number implements IMathUnit{
+    private double value;
+
+    public static final int TYPE_NUMBER = 20;
+    private static final char CHAR_0 = '0';
+    private static final char CHAR_1 = '1';
+    private static final char CHAR_2 = '2';
+    private static final char CHAR_3 = '3';
+    private static final char CHAR_4 = '4';
+    private static final char CHAR_5 = '5';
+    private static final char CHAR_6 = '6';
+    private static final char CHAR_7 = '7';
+    private static final char CHAR_8 = '8';
+    private static final char CHAR_9 = '9';
+    private static final char CHAR_POINT = '.';
+    private static final char CHAR_EXPONENT = 'E';
+
+    //КОНСТРУКТОР
+    public Number(String stringValue) {
+        value = Double.parseDouble(stringValue);
+    }
+    Number(double value) {
+        this.value = value;
+    }
+
+    //ИМПЛЕМЕНТАЦИЯ: IMathUnit
+    @Override
+    public int getType() {
+        return TYPE_NUMBER;
+    }
+
+    //МЕТОДЫ КЛАССА
+    //GETTER: value
+    public double getValue() {
+        return value;
+    }
+    //Проверяет является ли символ частью числа
+    public static boolean isNumberPart(char c) {
+        return c == CHAR_0 ||
+               c == CHAR_1 ||
+               c == CHAR_2 ||
+               c == CHAR_3 ||
+               c == CHAR_4 ||
+               c == CHAR_5 ||
+               c == CHAR_6 ||
+               c == CHAR_7 ||
+               c == CHAR_8 ||
+               c == CHAR_9 ||
+               c == CHAR_POINT ||
+               c == CHAR_EXPONENT;
+    }
+}