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I want to find a function (could be user-defined) from an expression based on pattern matching. However, I do not know the exact name (Head) of the function but know only the first few characters.

Say

expr= 2 x + x^2 FunC[1,x] + x^3 FunC[2,x];

Now if I knew the full name of the function (in this case FunC), then I could do something like

Cases[expr,_FunC,All]

{FunC[1, x], FunC[2, x]}

to access the occurrence of FunC.

However, say I do not know the full name/Head of the pattern, I know that it starts with Fun (or ends with unC). In that case, how do I access the occurrence of FunC in the expression using part of the Head?

Something like

 Cases[expr,_pattern_,All]

where _pattern_ could be part of the actual name/Head like Fun, unC.

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2 Answers 2

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Maybe something like this:

Cases[expr, _?(StringMatchQ[ToString[Head[#]], "Fun*"] &), All]
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expr = 2 x + x^2 MyFun1[1, x] + x^3 MyFun2[2, x]; p = Position[expr, x_ /; StringMatchQ[ToString[x], "My*"], {}, Heads -> False]

{{2, 2}, {3, 2}}

Extract[expr, p]

{MyFun1[1, x], MyFun2[2, x]}

q = Position[expr, x_ /; StringMatchQ[ToString[x], "My*"], {-1}]

{{2, 2, 0}, {3, 2, 0}}

Extract[expr, q]

{MyFun1, MyFun2}

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