Tests and Operators Guide¶

Tests and operators enable conditional logic and comparisons in templates. Miya Engine provides comprehensive operator support and 26+ test expressions with 100% Jinja2 compatibility.

Working Example: See examples/features/tests-operators/ for complete examples.

Table of Contents¶

Operators
Arithmetic Operators
Comparison Operators
Logical Operators
Membership Operators
Test Expressions
Type Tests
Container Tests
Numeric Tests
String Tests
Comparison Tests
Practical Examples

Operators¶

Arithmetic Operators¶

Perform mathematical operations:

Operator	Description	Example	Result
`+`	Addition	`{{ 5 + 3 }}`	`8`
`-`	Subtraction	`{{ 10 - 4 }}`	`6`
`*`	Multiplication	`{{ 6 * 7 }}`	`42`
`/`	Division	`{{ 15 / 3 }}`	`5.0`
`//`	Floor Division	`{{ 17 // 5 }}`	`3`
`%`	Modulo	`{{ 17 % 5 }}`	`2`
`**`	Power	`{{ 2 ** 8 }}`	`256`
`~`	String Concat	`{{ "Hello" ~ " " ~ "World" }}`	`"Hello World"`

Examples:

{# Basic arithmetic #}
<p>Total: ${{ price * quantity }}</p>
<p>Average: {{ total / count }}</p>
<p>Remaining: {{ 100 - used }}</p>

{# Floor division for whole numbers #}
<p>Pages: {{ total_items // items_per_page }}</p>

{# Modulo for even/odd #}
<p class="{{ 'even' if item_num % 2 == 0 else 'odd' }}">

{# Power for calculations #}
<p>Area: {{ radius ** 2 * 3.14159 }}</p>

{# String concatenation #}
<p>{{ first_name ~ " " ~ last_name }}</p>
<p>{{ "Total: $" ~ price|string }}</p>

Comparison Operators¶

Compare values:

Operator	Description	Example	Result
`==`	Equal to	`{{ 5 == 5 }}`	`true`
`!=`	Not equal to	`{{ 5 != 3 }}`	`true`
`<`	Less than	`{{ 3 < 5 }}`	`true`
`<=`	Less or equal	`{{ 5 <= 5 }}`	`true`
`>`	Greater than	`{{ 7 > 3 }}`	`true`
`>=`	Greater or equal	`{{ 5 >= 5 }}`	`true`

Examples:

{# Price comparisons #}
{% if product.price < 100 %}
  <span class="affordable">Affordable</span>
{% endif %}

{# Stock checks #}
{% if product.stock > 0 %}
  <button>Add to Cart</button>
{% else %}
  <span>Out of Stock</span>
{% endif %}

{# Age verification #}
{% if user.age >= 18 %}
  <p>Access granted</p>
{% endif %}

{# Equality checks #}
{% if user.role == "admin" %}
  <a href="/admin">Admin Panel</a>
{% endif %}

{# Inequality #}
{% if current_page != total_pages %}
  <a href="?page={{ current_page + 1 }}">Next</a>
{% endif %}

Logical Operators¶

Combine boolean expressions:

Operator	Description	Example	Result
`and`	Logical AND	`{{ true and true }}`	`true`
`or`	Logical OR	`{{ true or false }}`	`true`
`not`	Logical NOT	`{{ not false }}`	`true`

Examples:

{# AND - all conditions must be true #}
{% if user.active and user.verified %}
  <p>Full access granted</p>
{% endif %}

{% if product.price < 100 and product.stock > 0 %}
  <button>Buy Now</button>
{% endif %}

{# OR - any condition can be true #}
{% if user.role == "admin" or user.role == "moderator" %}
  <a href="/manage">Management</a>
{% endif %}

{# NOT - negate condition #}
{% if not user.blocked %}
  <p>Welcome!</p>
{% endif %}

{# Complex combinations #}
{% if (user.active and user.verified) or user.role == "admin" %}
  <p>Account is valid</p>
{% endif %}

{% if user.age >= 18 and (user.verified or user.trusted) %}
  <p>Access granted</p>
{% endif %}

Operator Precedence: 1. not 2. and 3. or

Use parentheses () to control order:

{# Different results based on grouping #}
{{ true or false and false }}    → true  (and first)
{{ (true or false) and false }}  → false (or first)

Membership Operators¶

Test membership in collections:

Operator	Description	Example	Result
`in`	Is member of	`{{ 3 in [1, 2, 3] }}`	`true`
`not in`	Is not member	`{{ 10 not in [1, 2, 3] }}`	`true`

Examples:

{# List membership #}
{% if "admin" in user.roles %}
  <p>Admin access</p>
{% endif %}

{# String contains #}
{% if "error" in message|lower %}
  <div class="alert-danger">{{ message }}</div>
{% endif %}

{# Not in #}
{% if product.id not in purchased_ids %}
  <button>Add to Cart</button>
{% else %}
  <span>Already Purchased</span>
{% endif %}

{# Check tag presence #}
{% if "featured" in product.tags %}
  <span class="badge">Featured</span>
{% endif %}

Test Expressions¶

Tests use the is syntax to check conditions:

{{ value is test_name }}
{{ value is test_name(argument) }}
{{ value is not test_name }}

Type Tests¶

Check variable types:

Test	Description	Example
`defined`	Variable exists	`{{ user is defined }}`
`undefined`	Variable doesn't exist	`{{ foo is undefined }}`
`none`	Value is None/null	`{{ value is none }}`
`boolean`	Is boolean	`{{ true is boolean }}`
`string`	Is string	`{{ "text" is string }}`
`number`	Is number	`{{ 42 is number }}`
`integer`	Is integer	`{{ 42 is integer }}`
`float`	Is float	`{{ 3.14 is float }}`

Examples:

{# Check if variable exists #}
{% if user is defined %}
  <p>Welcome, {{ user.name }}!</p>
{% else %}
  <p>Please log in</p>
{% endif %}

{# Check for null/none #}
{% if error_message is none %}
  <p>No errors</p>
{% else %}
  <div class="alert">{{ error_message }}</div>
{% endif %}

{# Type checking #}
{% if value is string %}
  <p>Text: {{ value }}</p>
{% elif value is number %}
  <p>Number: {{ value }}</p>
{% endif %}

{# Integer vs float #}
{% if price is integer %}
  ${{ price }}
{% else %}
  ${{ price|round(2) }}
{% endif %}

Container Tests¶

Check container types:

Test	Description	Example
`sequence`	Is list/tuple	`{{ [1,2,3] is sequence }}`
`mapping`	Is dictionary	`{{ {} is mapping }}`
`iterable`	Can be iterated	`{{ "text" is iterable }}`

Examples:

{# Check if iterable #}
{% if items is iterable %}
  <ul>
  {% for item in items %}
    <li>{{ item }}</li>
  {% endfor %}
  </ul>
{% endif %}

{# Dictionary check #}
{% if config is mapping %}
  {% for key, value in config.items() %}
    <p>{{ key }}: {{ value }}</p>
  {% endfor %}
{% endif %}

{# Sequence check #}
{% if data is sequence %}
  <p>List with {{ data|length }} items</p>
{% endif %}

Numeric Tests¶

Tests for numbers:

Test	Description	Example
`even`	Is even number	`{{ 4 is even }}` → `true`
`odd`	Is odd number	`{{ 5 is odd }}` → `true`
`divisibleby(n)`	Divisible by n	`{{ 15 is divisibleby(3) }}` → `true`

Examples:

{# Alternating row colors #}
{% for item in items %}
  <tr class="{{ 'even-row' if loop.index is even else 'odd-row' }}">
    <td>{{ item }}</td>
  </tr>
{% endfor %}

{# Check divisibility #}
{% if total is divisibleby(10) %}
  <p>Exact multiple of 10</p>
{% endif %}

{# Odd/even logic #}
{% if page_num is odd %}
  <div class="right-page">{{ content }}</div>
{% else %}
  <div class="left-page">{{ content }}</div>
{% endif %}

String Tests¶

Tests for strings:

Test	Description	Example
`lower`	All lowercase	`{{ "hello" is lower }}` → `true`
`upper`	All uppercase	`{{ "HELLO" is upper }}` → `true`
`startswith(s)`	Starts with string	`{{ "Hello" is startswith("He") }}` → `true`
`endswith(s)`	Ends with string	`{{ "World" is endswith("ld") }}` → `true`

Examples:

{# File type checking #}
{% if filename is endswith(".pdf") %}
  <span class="icon-pdf">{{ filename }}</span>
{% elif filename is endswith(".jpg") or filename is endswith(".png") %}
  <img src="{{ filename }}" alt="Image">
{% endif %}

{# URL protocol check #}
{% if url is startswith("https://") %}
  <span class="secure-badge">Secure</span>
{% endif %}

{# Case validation #}
{% if code is upper %}
  <p>Valid product code: {{ code }}</p>
{% else %}
  <p class="error">Code must be uppercase</p>
{% endif %}

Comparison Tests¶

Alternative comparison syntax:

Test	Description	Example
`equalto(value)`	Equal to value	`{{ 5 is equalto(5) }}` → `true`
`sameas(value)`	Identity check	`{{ true is sameas(true) }}` → `true`

Examples:

{# Equality test #}
{% if status is equalto("active") %}
  <span class="badge-success">Active</span>
{% endif %}

{# Same as - stricter than == #}
{% if value is sameas(true) %}
  <p>Explicitly true</p>
{% endif %}

Negated Tests¶

Use is not to negate any test:

{# Not defined #}
{% if error is not defined %}
  <p>No errors</p>
{% endif %}

{# Not none #}
{% if user.email is not none %}
  <p>Email: {{ user.email }}</p>
{% endif %}

{# Not even (i.e., odd) #}
{% if number is not even %}
  <p>{{ number }} is odd</p>
{% endif %}

{# Not empty #}
{% if items is not empty %}
  <p>Found {{ items|length }} items</p>
{% endif %}

Practical Examples¶

Example 1: User Access Control¶

{% if user is defined and user.active %}
  {% if user.role == "admin" %}
    <div class="admin-panel">
      <h2>Admin Dashboard</h2>
      <p>Full system access</p>
    </div>
  {% elif user.role == "moderator" %}
    <div class="mod-panel">
      <h2>Moderator Tools</h2>
      <p>Content management access</p>
    </div>
  {% elif user.verified and user.age >= 18 %}
    <div class="user-panel">
      <h2>User Dashboard</h2>
      <p>Standard access</p>
    </div>
  {% else %}
    <div class="restricted">
      <p>Limited access - please verify your account</p>
    </div>
  {% endif %}
{% else %}
  <div class="login-prompt">
    <p>Please log in to continue</p>
  </div>
{% endif %}

Example 2: Product Display¶

{% for product in products %}
  <div class="product-card">
    <h3>{{ product.name }}</h3>
    <p>${{ product.price }}</p>

    {# Stock status #}
    {% if product.stock > 0 %}
      {% if product.stock < 10 %}
        <p class="warning">Only {{ product.stock }} left!</p>
      {% else %}
        <p class="success">In Stock</p>
      {% endif %}
      <button>Add to Cart</button>
    {% else %}
      <p class="error">Out of Stock</p>
      <button disabled>Notify Me</button>
    {% endif %}

    {# Discount badge #}
    {% if product.discount is defined and product.discount > 0 %}
      <span class="badge">{{ product.discount }}% OFF</span>
    {% endif %}

    {# Featured #}
    {% if "featured" in product.tags %}
      <span class="star"> Featured</span>
    {% endif %}
  </div>
{% endfor %}

Example 3: Form Validation Display¶

<form>
  {# Username field #}
  <div class="form-group">
    <label>Username</label>
    <input type="text" name="username" value="{{ username|default('') }}">
    {% if errors.username is defined %}
      <span class="error">{{ errors.username }}</span>
    {% endif %}
  </div>

  {# Email field #}
  <div class="form-group">
    <label>Email</label>
    <input type="email" name="email" value="{{ email|default('') }}">
    {% if errors.email is defined %}
      <span class="error">{{ errors.email }}</span>
    {% elif email is defined and "@" not in email %}
      <span class="warning">Email looks invalid</span>
    {% endif %}
  </div>

  {# Age field #}
  <div class="form-group">
    <label>Age</label>
    <input type="number" name="age" value="{{ age|default('') }}">
    {% if age is defined %}
      {% if age is not number %}
        <span class="error">Must be a number</span>
      {% elif age < 18 %}
        <span class="error">Must be 18 or older</span>
      {% endif %}
    {% endif %}
  </div>

  <button type="submit">Submit</button>
</form>

Example 4: Data Table with Highlighting¶

<table>
  <thead>
    <tr>
      <th>ID</th>
      <th>Name</th>
      <th>Amount</th>
      <th>Status</th>
    </tr>
  </thead>
  <tbody>
  {% for row in data %}
    <tr class="{{ 'highlight' if row.amount > 1000 else '' }}
               {{ 'even' if loop.index is even else 'odd' }}">
      <td>{{ row.id }}</td>
      <td>{{ row.name }}</td>
      <td>
        {% if row.amount is divisibleby(100) %}
          <strong>${{ row.amount }}</strong>
        {% else %}
          ${{ row.amount }}
        {% endif %}
      </td>
      <td>
        {% if row.status is equalto("completed") %}
          <span class="badge-success"> Completed</span>
        {% elif row.status is equalto("pending") %}
          <span class="badge-warning"> Pending</span>
        {% else %}
          <span class="badge-danger"> Failed</span>
        {% endif %}
      </td>
    </tr>
  {% endfor %}
  </tbody>
</table>

Example 5: Complex Conditional Logic¶

{% for order in orders %}
  <div class="order">
    <h3>Order #{{ order.id }}</h3>

    {# Multi-condition status #}
    {% if order.paid and order.shipped and order.delivered %}
      <span class="badge-success"> Complete</span>
    {% elif order.paid and order.shipped %}
      <span class="badge-info"> In Transit</span>
    {% elif order.paid %}
      <span class="badge-warning"> Processing</span>
    {% else %}
      <span class="badge-danger"> Payment Required</span>
    {% endif %}

    {# Priority indicator #}
    {% if order.priority is defined and order.priority is upper %}
      <span class="priority-badge">{{ order.priority }}</span>
    {% endif %}

    {# Total calculation #}
    {% if order.total is number and order.total > 0 %}
      <p>Total: ${{ order.total|round(2) }}</p>

      {% if order.total >= 100 %}
        <p class="success"> Free shipping applied</p>
      {% elif order.total > 50 %}
        <p class="info">Add ${{ (100 - order.total)|round(2) }} for free shipping</p>
      {% endif %}
    {% endif %}
  </div>
{% endfor %}

Complete Reference¶

Operators Summary¶

Category	Operators	Example
Arithmetic	`+`, `-`, ``, `/`, `//`, `%`, `*`, `~`	`{{ 5 + 3 }}`
Comparison	`==`, `!=`, `<`, `<=`, `>`, `>=`	`{{ age >= 18 }}`
Logical	`and`, `or`, `not`	`{{ a and b }}`
Membership	`in`, `not in`	`{{ x in list }}`

Tests Summary¶

Category	Tests	Count
Type	defined, undefined, none, boolean, string, number, integer, float	8
Container	sequence, mapping, iterable, callable	4
Numeric	even, odd, divisibleby	3
String	lower, upper, startswith, endswith, match, alpha, alnum	7
Comparison	equalto, sameas, in, contains	4
TOTAL		26+ Tests

Best Practices¶

1. Use Tests for Type Checking¶

{#  Good - explicit type test #}
{% if value is defined and value is not none %}
  {{ value }}
{% endif %}

{#  Avoid - implicit truthiness can be unclear #}
{% if value %}
  {{ value }}
{% endif %}

2. Combine Operators Clearly¶

{#  Good - clear with parentheses #}
{% if (user.active and user.verified) or user.role == "admin" %}

{#  Avoid - precedence unclear #}
{% if user.active and user.verified or user.role == "admin" %}

3. Use Appropriate Tests¶

{#  Good - use even test #}
{% if number is even %}

{#  Avoid - manual modulo #}
{% if number % 2 == 0 %}

Summary¶

Complete operator and test support - 100% Jinja2 Compatible

All Operators: - Arithmetic: +, -, *, /, //, %, **, ~ - Comparison: ==, !=, <, <=, >, >= - Logical: and, or, not - Membership: in, not in

26+ Tests: - Type tests (defined, none, string, number, etc.) - Container tests (sequence, mapping, iterable) - Numeric tests (even, odd, divisibleby) - String tests (lower, upper, startswith, endswith) - Comparison tests (equalto, sameas) - All tests support negation with is not

All operators and tests work identically to Jinja2, providing powerful conditional logic for templates.

Tests and Operators Guide¶

Table of Contents¶

Operators¶

Arithmetic Operators¶

Comparison Operators¶

Logical Operators¶

Membership Operators¶

Test Expressions¶

Type Tests¶

Container Tests¶

Numeric Tests¶

String Tests¶

Comparison Tests¶

Negated Tests¶

Practical Examples¶

Example 1: User Access Control¶

Example 2: Product Display¶

Example 3: Form Validation Display¶

Example 4: Data Table with Highlighting¶

Example 5: Complex Conditional Logic¶

Complete Reference¶

Operators Summary¶

Tests Summary¶

Best Practices¶

1. Use Tests for Type Checking¶

2. Combine Operators Clearly¶

3. Use Appropriate Tests¶

See Also¶

Summary¶