\xleftharpoondown{abc}The command \xleftharpoondown{abc} is used in LaTeX to create an extensible arrow with a left harpoon pointing downwards over the text 'abc'. This is typically used in mathematical expressions to denote specific types of mappings or transformations, especially in fields like chemistry or physics where such notation is common.
Denotes a transformation from A to B with a left harpoon arrow.
\xleftharpoondown{A} \to BUsed in chemical equations to indicate the direction of a reaction.
\xleftharpoondown{\text{reactants}} \to \text{products}Represents a function f mapping from set X to set Y with a left harpoon arrow.
\xleftharpoondown{f} : X \to Y