Inverted syntax: Difference between revisions

In fact, using a Lisp-style macro, we can perform this transformation at parse time:

<lang factor>MACRO: pre ( quot -- quot ) reverse ;

[ + 2 2 ] pre ! 4</lang>

Of course, this isn't true prefix because <code>+</code> retains its arity of <tt>2</tt>:

<lang factor>[ + 3 + 2 2 ] pre ! 7</lang>

We can define a more accurate prefix macro for addition and subtraction in terms of <code>reduce</code>:

<lang factor>MACRO: pre ( quot -- quot ) 1 cut swap [ 0 ] dip reduce 1quotation ;

[ + 1 2 3 4 5 ] pre ! 15</lang>

Additionally, using parsing words, we can add any syntax we like. The <code>infix</code> vocabulary is an example of this: