pattern ~master

Pattern

Templated types for string pattern matching and lexers.

Pattern can be used to construct elaborate and complex pattern matchers that can operate at compile time (std.regex currently cannot), and are often faster than both regex and ctRegex matchers. Pattern was designed with lexers in mind.

Hello World

import pattern;

void main()
{
    // A pattern for lowercase letters.
    auto letters = repeat!(bracket!('a', 'z'));

    assert(letters("hello world") == "hello");
}

Patterns can also be defined from callback functions that accept either string or char and return bool.

import std.ascii : isWhite;

string whitespace(string input)
{
    // A pattern for whitespaces.
    enum pattern = repeat!isWhite;

    return pattern(input);
}

Pattern Types

Here's a short list of pattern types and concise examples of how they behave.

Primitive

void keyword()
{
    // A pattern that matches 'this' or 'that'
    enum p = primitive!("this", "that");

    assert(p("this") == "this");
    assert(p("them") is null);
}

Bracket

void numeric()
{
    // A pattern that behaves like /[0-9]/
    enum p = bracket!('0', '9');

    assert(p("123") == "1");
    assert(p("abc") is null);
}

Complement

void nonNumeric()
{
    // A pattern that behaves like /[^0-9]/
    enum p = complement!(bracket!('0', '9'));

    assert(p("123") is null);
    assert(p("abc") == "a");
}

Repeat

void integer()
{
    // A pattern that behaves like /[0-9]+/
    enum p = repeat!(bracket!('0', '9'));

    assert(p("123") == "123");
    assert(p("abc") is null);
}

Optional

void mightBeInt()
{
    // A pattern that behaves like /[0-9]?/
    enum p = optional!(bracket!('0', '9'));

    assert(p("123") == "123");
    assert(p("abc") == "");
}

Sequence

void decimal()
{
    // A pattern that behaves like /[0-9]\.[0-9]/
    enum p = sequence!(
        bracket!('0', '9'),
        primitive!("."),
        bracket!('0', '9')
    );

    assert(p("1.5") == "1.5");
    assert(p("1.b") is null);
    assert(p("5")   is null);
}

Selection

void intOrName()
{
    // A pattern that behaves like /[0-9]+|[a-z]+/
    enum p = selection!(
        repeat!(bracket!('0', '9')),
        repeat!(bracket!('a', 'z'))
    );

    assert(p("123") == "123");
    assert(p("abc") == "abc");
}

License

MIT