if - then ") ▁and ▁IF TE ▁(" if - then - else ") ▁functions . ▁ ▁I FT ▁and ▁IF TE ▁pop ▁two ▁or ▁three ▁commands ▁off ▁the ▁stack , ▁respectively . ▁ ▁The ▁top most ▁value ▁is ▁evaluated ▁as ▁a ▁boolean ▁and , ▁if ▁true , ▁the ▁second ▁top most ▁value ▁is ▁pushed ▁back ▁on ▁the ▁stack . ▁ ▁IF TE ▁allows ▁a ▁third ▁" else " ▁value ▁that ▁will ▁be ▁pushed ▁back ▁on ▁the ▁stack ▁if ▁the ▁boolean ▁is ▁false . ▁ ▁The ▁following ▁example ▁uses ▁the ▁I FT ▁function ▁to ▁pop ▁an ▁object ▁from ▁the ▁bottom ▁of ▁the ▁stack ▁and , ▁if ▁it ▁is ▁equal ▁to ▁ 1 , ▁rep laces ▁it ▁with ▁" One ": ▁▁▁ ▁« ▁ 1 ▁== ▁" One " ▁I FT ▁» ▁ ▁The ▁following ▁example ▁uses ▁the ▁IF TE ▁function ▁to ▁pop ▁an ▁object ▁from ▁the ▁bottom ▁of ▁the ▁stack ▁and , ▁if ▁it ▁is ▁equal ▁to ▁ 1 , ▁rep laces ▁it ▁with ▁" One ". ▁ ▁If ▁it ▁does ▁not ▁equal ▁ 1 , ▁it ▁rep laces ▁it ▁with ▁the ▁string ▁" Not ▁one ": ▁▁▁ ▁« ▁ 1 ▁== ▁" One " ▁" Not ▁one " ▁IF TE ▁» ▁ ▁I FT ▁and ▁IF TE ▁will ▁evaluate ▁a ▁program ▁block ▁given ▁as ▁one ▁of ▁its ▁arguments , ▁allowing ▁a ▁more ▁compact ▁form ▁of ▁conditional ▁logic ▁than ▁an ▁IF / TH EN / EL SE / END ▁structure . ▁ ▁The ▁following ▁example ▁pop s ▁an ▁object ▁from ▁the ▁bottom ▁of