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%mathpiper
/*
This is the beginnings of a Kind function which will return:
1) If u is an atomic expression, return the type of the expression.
2) If u is a compund expression, return the operator at the root of the
expression tree.
pp.104 "Computer Algebra And Symbolic Computation: Elementary Algorithms" Cohen.
*/
Retract("Kind",*);
RuleBase("Kind",{u});
//HoldArg("Kind",u);
10 # Kind(_u) <--
[
Write(u,,);
Local(result);
if(IsInteger(u))
[
result := integer;
Echo(1);
]
else if(IsString(u))
[
result := string;
Echo(2);
]
else if(IsList(u))
[
result := list;
Echo(3);
]
else if(Not IsBound(Eval(u)))
[
result := symbol;
Echo(10);
]
else
[
];
result;
];
Kind({3});
%/mathpiper
%output,preserve="false"
Result: list
Side Effects:
{3},3
. %/output
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