WolframLang: Add Element to List

By Xah Lee. Date: 2022-07-04. Last updated: 2024-06-07.

Almost all Functions do not modify the argument or variable. They return a new value. If you want to modify the variable that hold a list, you assign it back. e.g. listVar = f[ listVar ]
Function whose name end in “To”, (e.g. AppendTo) modifies the variable. (the argument must be a variable.)

Insert

Insert[list, elem, n]

Insert an element at n

same as Insert[list, elem, {n}]

Insert[ {3, 4}, x, 2 ] === {3, x, 4}

Insert[list, elem, {i, j, k}]

Insert[ {3, 4}, x, {2} ] === {3, x, 4}
Insert[ {3, {4}}, x, {2,1} ] === {3, {x, 4}}

Insert[list, elem, {pos1, pos2, etc }]

insert an element at several positions

Insert[ {{1,0}, {2,0}, {3,0}}, x, {{2}, {3,1}} ] === {{1, 0}, x, {2, 0}, {x, 3, 0}}

Append[expr, new]

return a new expr with new item added at end.

Append[ List[ 3, 4 ], 5 ] === {3, 4, 5}

AppendTo[x, elem]

Same as x=Append[x, elem]

Prepend

Add to beginning

Prepend[ List[ 3, 4 ], 5 ] === { 5, 3, 4}

PrependTo[x, elem]

Same as x=Prepend[x, elem]