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95 lines
2.2 KiB
ReStructuredText
95 lines
2.2 KiB
ReStructuredText
Functions
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=========
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Overall Structure
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-----------------
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As for other languages, functions allow to factorize code. In UWrap, they are
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meant to be used for expressions. The overall syntax is:
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.. code-block:: text
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function <name> (<parameters>) do
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<commands>
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end;
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The commands in a function need to be ``pick`` commands (as opposed to ``wrap``
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or ``weave`` which are no meaning in this context). When called in a context of
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a regular call, the first picked value will be returned. When called in the
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context of a generator, values will be generated following the same order as
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the overall of order of command evaluation.
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For example:
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.. code-block:: text
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function F () do
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pick "Hello ";
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then
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pick "World";
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end;
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Will either return "Hello " in a regular call, or "Hello " then "World".
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Functions can then be called in expressions, e.g.
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.. code-block:: text
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function add_space (p) do
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pick p & " ";
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end;
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wrap T (v => add_space (@));
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Generators
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----------
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All functions are generators - some only yield one value, some may yield
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several, but they all can be used as prefix or various suffixes supporting
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generators, such as ``all``, ``fold`` or ``filter``.
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For example, the following function:
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.. code-block:: text
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function F () do
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pick "Hello ";
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then
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pick "World";
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end;
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Yields "Hello " and "World. Functions call themselves call generator. In order
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or all values of a called generator to be yeiled, the suffix ``all`` need to
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be used both in the function and its caller. For example:
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.. code-block:: text
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function F1 () do
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pick child ();
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end;
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Will only pick the first child of the current iterator. But:
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.. code-block:: text
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function F2 () do
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pick child ().all();
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end;
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Will be able to generate all values. If called outide of the need of a
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gernerator though, only the first value will be picked, so the two calls below
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are equivalent:
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.. code-block:: text
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pick F1 () wrap X ();
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pick F2 () wrap X ();
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However, with e.g. a ``all`` suffix, F1 will only apply the X wrapper on the
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first child (it only yeilds one) while F2 will do on all:
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.. code-block:: text
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pick F1 ().all () wrap X ();
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pick F2 ().all () wrap X ();
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