Why am I getting this error $"/$usr$/$bin$/$ld: $/$tmp$/$gplcUNE$5$Eh$.$o: in function $`$predicate$($sibling$\_$of$/2)\text{'}$:

$(.$text$+0$xf$38)$: undefined reference to $`$predicate$($not$/1)\text{'}$

collect$2$: error: ld returned $1$ exit status"?

Here is my code:

$/*$ Database for family tree. It consists of facts and rules. $*/$

$/*$ The section in the highlighted box above has been completed for you $*/$

$/*$ Facts $*/$

$/*$ MALES $*/$

male$($abe$).$

male$($rob$).$

male$($jim$).$

male$($mac$).$

male$($bud$).$

male$($ben$).$

male$($kai$).$

male$($lee$).$

male$($roy$).$

male$($tex$).$

$/*$ FEMALES $*/$

female$($joy$).$

female$($ana$).$

female$($mia$).$

female$($kim$).$

female$($zoe$).$

female$($mae$).$

female$($amy$).$

female$($pam$).$

female$($val$).$

father$\_$of$($abe$,$ ana$)./*$ abe is the father of ana $*/$

father$\_$of$($abe$,$ rob$)./*$ abe is the father of rob $*/$

father$\_$of$($abe$,$ jim$)./*$ abe is the father of jim $*/$

father$\_$of$($jim$,$ mac$).$

father$\_$of$($jim$,$ kim$).$

father$\_$of$($bud$,$ zoe$).$

father$\_$of$($bud$,$ val$).$

father$\_$of$($bud$,$ tex$).$

father$\_$of$($bud$,$ roy$).$

father$\_$of$($ben$,$ bud$).$

father$\_$of$($ben$,$ amy$).$

father$\_$of$($kai$,$ lee$).$

father$\_$of$($kai$,$ pam$).$

mother$\_$of$($joy$,$ rob$)./*$ joy is the mother of rob $*/$

mother$\_$of$($joy$,$ jim$)./*$ joy is the mother of jim $*/$

mother$\_$of$($joy$,$ ana$)./*$ joy is the mother of ana $*/$

mother$\_$of$($mia$,$ mac$).$

mother$\_$of$($mia$,$ kim$).$

mother$\_$of$($ana$,$ zoe$).$

mother$\_$of$($ana$,$ val$).$

mother$\_$of$($ana$,$ tex$).$

mother$\_$of$($ana$,$ roy$).$

mother$\_$of$($mae$,$ amy$).$

mother$\_$of$($mae$,$ bud$).$

mother$\_$of$($amy$,$ lee$).$

mother$\_$of$($amy$,$ pam$).$

$/*$ Complete the facts given in the diagram above $*/$

$/*$ RULES $*/$

is$\_$male$($X$)$ :$-$

male$($X$)$;

father$\_$of$($X$,\_).$

is$\_$female$($X$)$:$-$

female$($X$)$;

mother$\_$of$($X$,\_).$

grandmother$\_$of$($X$,$Z$)$:$-$

parent$\_$of$($X$,$Y$),$

parent$\_$of$($Y$,$Z$),$female$($X$).$

grandfather$\_$of$($X$,$Z$)$:$-$

parent$\_$of$($X$,$Y$),$

parent$\_$of$($Y$,$Z$),$male$($X$).$

sibling$\_$of$($X$,$Y$)$:$-$

parent$\_$of$($Z$,$X$),$

parent$\_$of$($Z$,$Y$),$not$($X$=$Y$).$

parent$\_$of$($X$,$Y$)$:$-$

father$\_$of$($X$,$Y$)$;

mother$\_$of$($X$,$Y$),$male$($X$)$;female$($X$).$

descendent$\_$of$($X$,$Y$)$:$-$

parent$\_$of$($Y$,$X$).$

descendent$\_$of$($X$,$Y$)$ :$-$

parent$\_$of$($Y$,$ Z$),$ descendent$\_$of$($Z$,$X$).$