This macro implements a syntax that emulates Pythons [generator-expression] syntax in a form more compatible with rusts usual syntax.

This means that there a few small differences between the python syntax and the syntax prvided in this macro:

• The expression in the beginning of the generator expression must end with a semicolon (;).
• The pattern between the for and in tokens is a fully-fledged rust pattern, which can be as simple as a simple token and as complex as struct destructuring.
• The expression defining the iterator after the for token (and potentially before an if token) must evaluate to either an Iterator or an impl IntoIterator, and end with a semicolon (;).
• The conditional expression after the if expression expression (and potentially before a for token) must evaluate to a boolean, and end with a semicolon (;).

The expression replaced by the comp!() macro invocation is a lazy iterator whose lifetime is bound by any references it needs to capture. This means that it can be .collect()ed into any container you like.

Examples

Simple generator expression with a conditional: ```rust use py_comp::comp;

[derive(Debug, PartialEq, Eq)]

struct Foo(i32);

let arr = &[Foo(11), Foo(12)];

// Notice the semicolons let comp_vector = comp!(item; for item in arr; if item.0 % 10 == 2;) .collect::>();

asserteq!(compvector, vec![&Foo(12)]) ```

Triple cartesian product with conditions and patterns: ```rust use py_comp::comp;

[derive(Debug, PartialEq, Eq)]

struct Foo(i32);

// These need to be references to arrays because of how the closures // that the macro expands to capture their environment. let x = &[(Foo(11), "foo"), (Foo(12), "bar")]; let y = &[Foo(21), Foo(22)]; let z = &[Foo(31), Foo(32)];

let xyz = comp!( (a, b, c); for (a, _text) in x; // You can use any function parameter pattern. if a.0 % 10 == 2; for b in y; // Obviously not every level requires a conditional. for c in z; if c.0 % 10 == 2; ) .collect::

// The result vector here is short for illustration purposes // but can be as long as long as you need it to be. assert_eq!(xyz, vec![(&Foo(12), &Foo(21), &Foo(32)), (&Foo(12), &Foo(22), &Foo(32))]) ```