鉴于两个变量列表，ISO Prolog中最紧凑和规范的方法是什么来确定两者的结合？也就是说，我们需要（元逻辑）谓词的定义
varset_union(VarSet1, VarSet2, Union)
以及列表清单
varset_union(VarSets, Union)
其中Union是给定VarSet的唯一变量列表。
以下是ISO / IEC 13211-1：1995中的overview of the built-ins，包括Cor.2：2012。
答案 0 :(得分：13)
使用term_variables/2的解决方案：
varset_union(VarSet1, VarSet2, Union):-
term_variables([VarSet1|VarSet2], Union).
varset_union(VarSets, Union):-
term_variables(VarSets, Union).
使用setof/3的解决方案：
varset_union(VarSet1, Varset2, Union):-
varset_union([VarSet1, VarSet2], Union).
varset_union([], []).
varset_union(VarSets, Union):-
setof(Var, VarSet^(member(VarSet, VarSets), member(Var, VarSet)), Union).
答案 1 :(得分：2)
基于Tudor的好答案，我设计了一个 <html>
<head>
<script type="text/javascript">
function checkunit()
{
if(document.getElementById("unit2").value=="CK")
{
document.getElementById("unittype1").innerHTML='cm';
document.getElementById("unittype2").innerHTML='cm';
document.getElementById("unittype3").innerHTML='cm';
}
else
{
document.getElementById("unittype1").innerHTML='in';
document.getElementById("unittype2").innerHTML='in';
document.getElementById("unittype3").innerHTML='in';
}
}
function validatecal(form)
{
if (form.vm_length.value=="" || form.vm_length.value==0) {alert('Enter Length'); form.vm_length.focus(); return false}
if (!IsNumber(form.vm_length.value) && form.vm_length.value!="") {alert('Invalid Length'); form.vm_length.focus(); return false}
if (form.vm_width.value=="" || form.vm_width.value==0) {alert('Enter Width'); form.vm_width.focus(); return false}
if (!IsNumber(form.vm_width.value) && form.vm_width.value!="") {alert('Invalid Width'); form.vm_width.focus(); return false}
if (form.vm_height.value=="" || form.vm_height.value==0) {alert('Enter Height'); form.vm_height.focus(); return false}
if (!IsNumber(form.vm_height.value) && form.vm_height.value!="") {alert('Invalid Height'); form.vm_height.focus(); return false}
calcVolWeight();
return false;
}
function calcVolWeight() {
var lengthValue = document.getElementById("vm_length").value;
var widthValue = document.getElementById("vm_width").value;
var heightValue = document.getElementById("vm_height").value;
var weightDivisor = document.getElementById("unit2").value == "IP" ? 139 : 5000;
var roundFactor = document.getElementById("unit2").value == "IP" ? 1 : 0.5;
var originalVolume = lengthValue * widthValue * heightValue;
// Calculate the volumetric weight
var calcVolWeight = roundFactor * Math.ceil(( originalVolume / weightDivisor ) / roundFactor);
document.getElementById("total_weight").value = parseFloat(calcVolWeight);
}
</script>
</head>
<body>
<form name="vcalculator" id="vcalculator" method="post" onSubmit="return validatecal(this)">
<label >Select Units :</label>
<select name="unit2" id="unit2" onChange="checkunit()" >
<option value="CK">CM/KG</option>
<option value="IP">Inches/Pounds</option>
</select>
</div>
</div>
<label >Enter Dimensions :</label>
<label ">Length</label>
<input type="text" name="vm_length" id="vm_length" >
<span id="unittype1" >cm</span>
<label ">Width</label>
<input type="text" name="vm_width" id="vm_width" />
<span id="unittype2" >cm</span>
<label ">Height</label>
<input type="text" name="vm_height" id="vm_height" />
<span id="unittype3" >cm</span>
<label >Dimensional Weight :</label>
<input type="text"disabled="disabled"name="total_weight" id="total_weight" >
<input type="submit" value="Calculate" name="Submit"/>
<input type="reset" value="Clear" name="Submit2" />
</form>
</body>
</html>
的定义更紧凑 2个字符：
varset_union/3- ）