我正在攻读考试，我在书中遇到了prolog部分和这个问题。我想创建一个谓词＆评估＆＃39;当给定任何表达式时，将值设置为R. IE： <?php
$data = [
[
'company_code' => 'ABC',
'supplier_codes' => ['S-2','S-3','S-5'],
],
];
$database = [
'company_code' => 'ABC',
'suppliers' => [
[
'code' => 'S-1',
],
[
'code' => 'S-2',
'reference' => '12345'
],
[
'code' => 'S-3',
],
[
'code' => 'S-4',
'reference' => 'some string',
]
],
];
foreach($database['suppliers'] as $k=>$v){
foreach($data as $kd=>$vd){
$valueremove = false;
$removeIndex = '';
foreach($vd['supplier_codes'] as $key=>$val){
if($val == $v['code']){
$valueremove = false;
$removeIndex = '';
break;
} else {
$valueremove = true;
$removeIndex = $k;
}
}
if($valueremove == true){
unset($database['suppliers'][$removeIndex]);
} else {
$valueinsert = false;
foreach($data as $kd=>$vd){
foreach($vd['supplier_codes'] as $key=>$val){
foreach($database['suppliers'] as $kc=>$vc){
if($val == $vc['code']){
$valueinsert = false;
$insertIndex = '';
$insertVal = '';
break;
} else {
$valueinsert = true;
$insertIndex = count($database['suppliers'])+1;
$insertVal = $val;
}
}
if($valueinsert == true){
$database['suppliers'][$insertIndex] = array('code'=>$insertVal);
}
}
}
}
}
}
echo "<PRE>"; print_r($database);
它的计算结果为R = 400.我将如何创建它？
答案 0 :(得分：0)
正如@Dmitri Chubarov建议你可以使用is/2：
evaluate(X,R):- R is X.
以上简单地说R是X的算术结果，因此is/2进行所有算术运算并返回算术结果。
示例：
?- A=4,B=5, evaluate(((A*B)-2)/3,R).
A = 4,
B = 5,
R = 6.