Inverted syntax: Difference between revisions
→{{header|Factor}}: Be smarter about it with macros
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[ map [ sq ] { 1 2 3 4 5 } ] reverse call ! { 1 4 9 16 25 }</lang>
<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:
<lang factor>USE: infix
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