Mapping cone (homological algebra)
= Mapping cone
{disambiguate=homological algebra}
{title2=$M(f)$}
{wiki}
= Mapping cone
{synonym}
For a chain map $f:C\to C'$, one mapping-cone convention takes $M(f)_i=C_{i-1}\oplus C'_i$ with a differential combining $d,d'$ and $f$. Its short exact sequence with $C'$ and a shift of $C$ produces a long exact sequence in homology.