# TI-BASIC:Index Finder

**Routine Summary**

Returns the index number of an element searched for within a list

**Inputs**

*X* - Element that it's finding
*L₁* - List that's being searched

**Outputs**

*Ans* - Index number of element searched.

**Variables Used**

Variables not documented.

**Calculator Compatibility**

TI-83/84/+/SE/CSE
**Author**

RogueBantha**Authors**

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**Download**

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//Finds first occurence of X in L1 1+sum(not(cumSum(L1=X))) //Finds last occurence of X in L1 max((L1=X)cumSum(1 or L1))

Given a value in X, this code will search L1 and return the index number of the first (or last) occurrence of X. For example, in a list L1={1,2,5,4}, the index value of the element 5 is 3. Storing 5 to X and running this code will return 3.

# Error Conditions

The first routine returns 1+Dim(L₁) if L1 does not contain X, so if L1={1,2,5,4} and one searches for 9, the code will return 5.

The second routine returns 0 if L1 does not contain X, so L1={1,2,5,4} and one searches for 9, the code will return 0.