The diagram arrows are those arrows specially designed to fit nicely in a diagram; their variety and their names are the same as those of in-text arrows: plain arrow (+ar+), dotted arrow (+dotar+), monomorphism (+mono+), epimorphism (+epi+), bimorphism (+bimo+), isomorphism (+iso+), pair of parallel arrows (+biar+), equality (+eql+) and pair of adjoint arrows (+adjar+). You should never use an in-text arrow in a diagram nor a diagram arrow in a line of text: the technical characteristics of those pictures are just incompatible!
While an in-text arrow is always horizontal, the possibility must exist to give a diagram arrow a rather arbitrary direction. For that reason the name of a diagram arrow starts always with the prefix indicating its direction, even in the case of an horizontal right pointing arrow. The direction of an arrow is indicated by a direction of the compass-card, using the classical abbreviations:
llll north( +n+ )&south( +s+ )&east( +e+ )&west( +w+ )
The command for producing a primary arrow is obtained by typing the abbreviation for its direction followed by the abbreviation for the type of arrow. For example the command ++ will produce a west pointing bimorphism. Here are other examples. &bull#bullet; &bull#bullet; &bull#bullet; J &bull#bullet; &bull#bullet; &bull#bullet; &bull#bullet; &bull#bullet; &bull#bullet;
The case of adjoint arrows requires a comment. For east and west pairs of adjoint arrows, the direction is that of the lower arrow; for north and south pairs of adjoint arrows, the direction is that of the left arrow.
The standard length of a primary arrow is 50pt, but the length of an horizontal arrow is automatically adjusted when the adjacent vertices have too long names.