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Vision Reference

Table of Contents
Directives
Standard Library
- entities
- functional
- html
- util
- xhtml

Directives

Following is an alphabetical list of all directives in Vision, along with a brief description and a link to the corresponding section of the tutorial.

@chdir: Change the current working directory.
@day: Get the current day.
@define: Define a template.
@eval: Evaluate a string as Vision code.
@expand: Explicit expansion.
@export: Export an identifier to the enclosing scope.
@hour: Get the current hour.
@ifdef: Expand if an identifier is defined.
@ifndef: Expand if an identifier is not defined.
@include: Include a Vision file.
@local: Create a new local scope.
@minute: Get the current minute.
@month: Get the current month.
@quote: Escape shell characters.
@second: Get the current second.
@system: Execute a system command.
@unix: Execute a Unix command.
@windows: Execute a Windows command.
@year: Get the current year.

Standard Library

Vision has a growing standard library of templates to use for many common tasks. Their contents can be imported using the @include directive. These templates can be installed anywhere, but conventionally should be in a subdirectory named vision in the same directory as other page templates.

The standard library is arranged hierarchically based on dependencies, with many convenience headers.

entities

The entities family of headers defines HTML character entities as template variables, to improve legibility by allowing, for example, ' ' to be replaced with simply nbsp. The entities are divided into logical sections according to use:

entities/all: All other entities headers.
entities/accents: Accents and accented characters.
entities/arrows: Arrows. That's not a trick.
entities/greek: Greek characters.
entities/math: Mathematical symbols, plus arrows and greek.
entities/punct: Punctuation and symbols.
entities/sgml: SGML markup-significant characters.
entities/spacing: Spaces and modifiers, such as nbsp, zwj, and rlm.

functional

This is an experimental header and is subject to change.

The functional header defines templates for basic Boolean logic, which will be extended in the future by judicious additions of both built-in features and Vision-based combinations of those features.

The true and false templates are used to represent the corresponding truth values in Boolean logic. These templates must be used for truth values to ensure correct interpretation of the Boolean functions. There is no automatic conversion to Booleans.

The and, or, xor, and not templates produce the truth value corresponding to the result of the given Boolean operation on the one or two supplied arguments. For instance, and { true, true } returns true.

The if template expands the remainder of its content if its first parameter is true, e.g., if { true; 'Hello' } expands to Hello.

The defined template can be used to obtain a truth value for whether a variable is defined, e.g., defined:'var' evaluates to true if var is defined or false otherwise.

html

The html header defines a few miscellaneous templates that might commonly be used in HTML and XHTML documents. All identifiers are prefixed with html:.

stylesheet: Shorthand for linking to an external CSS stylesheet.
javascript: Shorthand for linking to an external Javascript file.

These templates are not for inline stylesheets or scripts. Use of such inline content in Vision is considered bad form.

@include 'vision/html';

html {
    head {
        title : 'Test';
        html:stylesheet : '/style.css';
        html:javascript : 'http://code.jquery.com/jquery-1.4.2.js';
    }
    body : '...';
}

util

util contains just a few utility templates.

null: An empty string, used to erase a variable or create an empty tag with both opening and closing parts.
group: Evaluates and returns its contents as a single value. Used to supply multiple elements to a template that accepts a limited number of arguments.
newline: A literal newline, in case you ever happen to need one.

xhtml

The xhtml header defines handy templates for generating XHTML documents. It also includes the util and html headers. All identifiers are prefixed with xhtml: for consistency.

strict: Creates a proper XHTML 1.0 Strict document.
transitional: Creates a proper XHTML 1.0 Transitional document.
strict:doctype: The DOCTYPE declaration for an XHTML 1.0 Strict document.
transitional:doctype: The DOCTYPE declaration for an XHTML 1.0 Transitional document.

@include 'vision/xhtml';

xhtml:strict {
    head {
        title : "ExampleCo";
    }
    body {
        "ExampleContent."
    }
}