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$\vdash$  \=$\forall$$S$, $T$:Type, $f$:($S$$\rightarrow$$T$), $b$:$\mathbb{B}$, $p$, $q$:$S$.\+
\\[0ex]$f$(if $b$ then $p$ else $q$ fi ) = if $b$ then $f$($p$) else $f$($q$) fi 
\-
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