Arrow symbols. \leftarrow \rightarrow \longleftarrow \longrightarrow \Leftarrow \Rightarrow \Longleftarrow \Longrightarrow \hookleftarrow \hookrightarrow \leftharpoonup \rightharpoonup \leftharpoondown \rightharpoondown \rightleftharpoons \leadsto \leftrightarrow \longleftrightarrow \Leftrightarrow \Longleftrightarrow \mapsto \longmapsto \uparrow \downarrow \Uparrow \Downarrow \updownarrow \Updownarrow \nearrow \searrow \swarrow \nwarrow