28.6.8 Removing spaces from strings: an example

Suppose you need to remove spaces and apostrophes from a string value (such as a topic title), and replace each space with an underscore, sending the result to output. The following macro uses several macro expression features:

[NewString]

<$_repeat ($$OldString length)>\

  <$$char = ($$OldString char $$_count)>\

  <$_if ($$char is " ")>_\

    <$_elseif ($$char is not "'"><$$char>\

    <$_endif>\

  <$_endrepeat>\

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