Sifr (صفر)

A modernized, deeply customizable Material 3 calculator for Android — published on the Google Play Store. Basic + scientific calculation, built-in converters, five hand-crafted palettes, and full right-to-left support across 11 languages. Named after the Arabic word for "zero" (the root of the English word "cipher" and the foundational concept of digital computing).

Screenshots

Five hand-crafted palettes — each with light & dark variants, plus Material You.

Layl neon-teal glass	Bayan ink color-block	Raqim editorial serif	Farah playful pills	Mizan machined keys

Scientific mode, built-in tools, history, and full Arabic (RTL).

Scientific	Tools	History	Settings	العربية

Features

Calculation

• Basic + scientific modes (toggle from the toolbar)
• Functions: sin, cos, tan, asin, acos, atan, ln, log, √, exp
• Constants: π, e
• Operators: +, −, ×, ÷, %, ^ (right-associative power), ! (factorial)
• Angle unit toggle: degrees ⇄ radians
• Implicit multiplication: 5sin(30), πe, 2(3+1) all parse as expected
• IEEE-754 precision cleanup: sin(30°) = 0.5, sin(π) = 0 (no trailing noise)
• Recursive-descent expression evaluator with operator precedence, parentheses, and unary minus

Editing

• Editable cursor — tap anywhere in the expression to position the cursor
• Range selection + Copy
• Live result preview while typing
• Auto-shrinking font for long expressions; one-tap "smart delete" peels whole function tokens (sin( → empty)

Memory + history

• Memory keys: MC, M+, M−, MR
• M-chip indicator when memory is non-empty
• Calculation history (Room-backed) — tap any past row to restore the expression

Tools (⊞ from the toolbar)

• Currency converter — live rates with an offline-first cache and bundled seed rates; searchable picker with flags
• Unit converter — length, weight, temperature, data
• Tip & split — preset percentages, per-person split
• Date calculator — difference between dates and add-days

Themes & personalization

• Five hand-crafted palettes — Layl, Bayan, Raqim, Farah, Mizan — each with light & dark variants
• Material You dynamic color
• Mode: light, dark, or follow-system
• Four keypad layouts: Classic, Remix, Arc, Tape
• Optional memory-key row

Settings

• In-app language switch (live, no restart) with a universal language anchor on the row
• Haptic feedback toggle (intent-based, not per-press)
• Error-sound toggle
• All preferences persisted via DataStore

Form factor + locale

• Adaptive landscape layout — scientific + basic blocks side by side
• Immersive landscape mode + an in-app rotate toggle
• 11 languages — English, Arabic, Spanish, Portuguese (BR), French, German, Indonesian, Turkish, Italian, Vietnamese, Russian
• Full right-to-left (RTL) coverage — interface, errors, in-app strings
• Five distinct localized error types (division by zero, invalid expression, function domain, overflow, syntax)

See CHANGELOG.md for the per-release breakdown.

Tech stack

• Language: Kotlin 2.3.21
• UI: Jetpack Compose, Material 3 (BOM 2026.05.00)
• Architecture: MVI with unidirectional data flow (State / Action / Event)
• DI: Koin 4.2.1
• Navigation: Jetpack Navigation 3 (1.1.1)
• Persistence: Room 2.8.4 (history) + DataStore 1.2.1 (settings)
• Feedback: Pulsar 1.1.0 (haptics + sound)
• Build: Gradle 9.5.0, AGP 9.2.1, JDK 21 toolchain (declarative via gradle/gradle-daemon-jvm.properties), Java 17 target
• Build scripts: Kotlin DSL with version catalog (gradle/libs.versions.toml)
• Testing: JUnit 4, Google Truth, Turbine, Espresso

Project structure

Single-module Gradle project — namespace dev.gaddal.sifr, applicationId com.gaddal.materialcalculator (intentionally distinct to preserve the live Play Store listing). Layered packages inside :app:

• core/ — cross-feature primitives
  • data/ — Room database, DataStore-backed SettingsRepository, cross-feature CalculatorInputBus
  • domain/ — Result<D, E>, CalcError, UiText, settings models
  • ui/ — theme, navigation routes, feedback controller, reusable UI utilities
• feature/ — user-facing surfaces, each with its own domain + ui packages
  • calculator/ — ExpressionWriter, ExpressionParser, ExpressionEvaluator, CalculatorViewModel, the keypad + display composables
  • history/ — Room-backed history list + tap-to-restore
  • settings/ — theme picker + feedback toggles

The calculation pipeline is one-shot per = press: UI emits a CalculatorAction, ExpressionWriter mutates the raw expression string (also handling cursor + range selection + implicit multiplication + smart delete), ExpressionParser tokenizes it into ExpressionParts (numbers, ops, constants, function names, postfix !), and ExpressionEvaluator evaluates with a hand-written recursive-descent grammar:

expression → term (± term)*
term       → factor (×|÷|% factor)*
factor     → power
power      → unary (^ power)?        // right-associative
unary      → -unary | postfix
postfix    → primary (!)*
primary    → number | constant | function(expression) | (expression)

For deeper architecture notes and conventions see CLAUDE.md.

Build

The project uses the Gradle wrapper. From the repo root:

# Debug APK
./gradlew :app:assembleDebug

# Install on connected device
./gradlew :app:installDebug

# All unit tests
./gradlew test

# Single test class
./gradlew :app:testDebugUnitTest --tests "dev.gaddal.sifr.feature.calculator.domain.ExpressionEvaluatorTest"

# Lint
./gradlew :app:lintDebug

# Signed release AAB (requires keystore in local.properties)
./gradlew :app:bundleRelease

Build variants

Three build types: debug, staging, release. Staging carries applicationIdSuffix .staging so it installs alongside the production build.

local.properties (gitignored) defines keystore.file, keystore.password, keystore.alias, keystore.alias_password for release signing. The build script wraps the read in runCatching, so missing or malformed local.properties (or just missing the keystore.* keys) only blocks release/staging signed builds — debug builds work without the keystore lines as long as sdk.dir (or ANDROID_HOME env var) is present.

Branching

feature/* → development → master

Work happens on feature/<name> branches off development. master is production-only and ships to Play Store; tags are cut from master only (e.g. v1.3.0). A staging branch + staging build variant exist in the build config and will be activated once CI is wired (planned for an upcoming phase).

Roadmap

Shipped to Play

• v1.2.0 (2026-05-09) — Phase 1: toolchain modernization, Material 3 dynamic color, edge-to-edge, error handling, Android 16 target SDK
• v1.3.0 (2026-05-12) — Phase 2.0 → 2.10: Sifr rebrand, MVI + Koin + Nav3 architecture, Settings, History, scientific mode + memory keys, adaptive landscape, editable cursor + live preview, haptic + sound feedback, typed errors with full EN + AR localization

Done in-repo, batched for the v2.0 cut

• Full visual redesign — five hand-crafted palettes + Material You, four keypad layouts, redesigned display with an in-line result tape
• Tools — currency (live + offline), unit, tip & split, and date converters
• History redesign — result-grouped rows, tap-to-restore, pinned clear-all
• Internationalization to 11 languages with an in-app live language switch (no restart)

Coming

• Google Play listing assets (icon, feature graphic, screenshots) and the v2.0 release
• GitHub Actions CI/CD (then activating the development → staging → master flow)
• Signed release / staging builds

Author

Built by Hussain Gaddal.

License

Sifr is source-available under the PolyForm Noncommercial License 1.0.0. You're welcome to read, learn from, and build on the code for noncommercial purposes; commercial use — including redistributing it or publishing a derivative on an app store — is not permitted. For a commercial license, contact the author.