Hi Khaled,
Neo Euler does not have all math arrows at the moment, if some one can come with a list of standard math arrows (i.e. CM and AMS ones), I'll see if I can add them.
I extracted the following list from the Tex Reference Card J.H. Silverman. Seeing as that card is for plain TeX, I'd assume his list of arrows is pretty standard. I don't know how much of a subset of all the arrows available in CM is, but it's a start. \longleftarrow \leftarrow or \gets \Longleftarrow \Leftarrow \longrightarrow \rightarrow or \to \Longrightarrow \Rightarrow \longleftrightarrow \leftrightarrow \Longleftrightarrow \Leftrightarrow \longmapsto \mapsto \hookleftarrow \uparrow \downarrow \updownarrow \nearrow \nwarrow \hookrightarrow \Uparrow \Downarrow \Updownarrow \searrow \swarrow Many thanks, Mathieu