Inverted syntax: Difference between revisions
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The word <code>'</code> alters the sequential flow by causing the item following it to be placed on the stack rather than being evaluated. The word <code>do</code> causes the item on the top of the stack to be evaluated. So we could define a new word, <code>if.1</code> with
<pre>[ swap do
which would allow us to use the syntax <code>' raining ' use-umbrella if.1</code>. (<code>iff</code> conditionally skips over two items, <code>else</code> unconditionally skips over one item.)
<code>'</code> is defined using the meta-control flow operator <code>]'[</code> thus: <code>[ ]'[ ] is '</code> Meta-control flow operators grant their behaviour to the word that calls them. So if we wanted the syntax <code>' use-umbrella if.2 raining</code> we could define <code>if.2</code> with
<pre>[ ]'[ do iff do else drop ] is if.2</pre>
Other syntaxes can be achieved by the judicious use of <code>'</code> and <code>]'[</code>. To demonstrate just one that avoids the use of <code>if ...</code> or <code>iff ... else ...</code> entirely, one could define a word <code>ifelse</code> as
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