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(make-If  true  X  Y)	   =>	X
(make-If  false  X  Y)	   =>	Y
(make-If  X  true  false)  =>	X
(make-If  X  Y  Y) 	   =>	Y
(make-If  X  Y  Z)	   =>	(make-If  X  Y\[X <\- true\]  Z\[X <\- false\])

Wiki MarkupThe notation {{M\[X <\- N\]}} means {{M}} with all occurrences of the symbol {{X}} replaced by the expression {{N}}. It is very costly to actually perform these subtitutions on =norm-if-form= data. To avoid this computational expense, we simply maintain a list of bindings which are pairs consisting of symbols (variable names) and boolean values { {{true}}, {{false}}. The following data definition definition formally defines the {{binding}} type.

A binding is a pair (make-binding s v) where s is a symbol (a variable) and v is a boolean value (an element of { true, false }.

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