<div class="notebook">

<div class="nb-cell markdown" name="md1">
## Example 1

Write a predicate `sum(X,S)` that is true when `S` is the sum of the elements of list `X`.
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<div class="nb-cell program" name="p1">
len([],0).
len([_|T], S) :- len(T,S1), S is S1 + 1.

sum([],0).
sum([H|T], S) :- sum(T,S1), S is S1 + H.
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<div class="nb-cell query" data-tabled="true" name="q1">
sum([],S)
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<div class="nb-cell query" data-tabled="true" name="q2">
sum([1,2,3,4,5],S)
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<div class="nb-cell html" name="htm1">

</div>

<div class="nb-cell markdown" name="md2">
## Problem 1

Write the predicate `prod(X,S)` that is true when `S` is the product of the elements of `X`.
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<div class="nb-cell program" name="p2">
prod([],1).
prod([H|T],P) :- prod(T,P1), P is P1 * H.

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<div class="nb-cell query" data-tabled="true" name="q3">
prod([],P).
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<div class="nb-cell query" data-tabled="true" name="q4">
prod([2,3,4,5,6],P).
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<div class="nb-cell markdown" name="md3">
## Problem 2

Create a preedicate `append(X,Y,Z)` that is true when `Z` is the result of appending lists `X` and `Y`.
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<div class="nb-cell program" name="p3">
append([],Z,Z).
append([H|T],Y,[H|Z]) :- append(T,Y,Z).
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<div class="nb-cell query" data-tabled="true" name="q5">
append([],[],Z).
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<div class="nb-cell query" data-tabled="true" name="q6">
append([1,2,3],[],Z)
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<div class="nb-cell query" data-tabled="true" name="q10">
append([],[3,5,7],S).
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<div class="nb-cell query" data-tabled="true" name="q7">
append([8,6,7],[5,3,0,9],Z).
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<div class="nb-cell markdown" name="md4">
## Problem 3

Write a predicate `isprefix(X,Z)` that is true when `X` is a prefix of `Z`.
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<div class="nb-cell program" name="p4">
/* Copy append code here */

isprefix(X,Z) :- append(X,_,Z).
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<div class="nb-cell query" data-tabled="true" name="q8">
isprefix([1,2],[1,2,3,4,5]).
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<div class="nb-cell query" data-tabled="true" name="q9">
isprefix([3,4],[1,2,3,4,5]).
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