\overleftharpoonup{text} \NC\NR
\NC \tex{overrightharpoondown} \NC \overrightharpoondown{text} \NC\NR
\NC \tex{overrightharpoonup} \NC \overrightharpoonup{text} \NC\NR
\TB
\NC \tex{underleftarrow} \NC \underleftarrow{text} \NC\NR
\NC \tex{underrightarrow}\NC
{text} \NC\NR
\NC \tex{texoverleftharpoondown} \NC \overleftharpoondown{text}\NC\NR
\NC \tex{overleftharpoonup} \NC \overleftharpoonup{text} \NC\NR
\NC \tex{overrightharpoondown} \NC \overrightharpoondown{text} \NC\NR
\NC \tex{overrightharpoonup} \NC \overrightharpoonup{text
{\overleftrightarrow{A}}$ $b_{\overleftrightarrow{ABC}}$
As an added bonus:
\definemathoverarrow [overtwoheadrightarrow] [\twoheadrightarrowfill]
\definemathoverarrow [overtwoheadleftarrow] [\twoheadleftarrowfill]
\definemathoverarrow [overrightharpoondown] [1pt] [\rightharpoondownfill
[overtwoheadrightarrow] [\twoheadrightarrowfill]
\definemathoverarrow [overtwoheadleftarrow] [\twoheadleftarrowfill]
\definemathoverarrow [overrightharpoondown] [1pt] [\rightharpoondownfill]
\definemathoverarrow [overrightharpoonup] [\rightharpoonupfill]
\definemathoverarrow
up in the core (including the added
bonus if possible ;).
As an added bonus:
\definemathoverarrow [overtwoheadrightarrow] [\twoheadrightarrowfill]
\definemathoverarrow [overtwoheadleftarrow] [\twoheadleftarrowfill]
\definemathoverarrow [overrightharpoondown] [1pt
]
\definemathoverarrow [overtwoheadleftarrow] [\twoheadleftarrowfill]
\definemathoverarrow [overrightharpoondown] [1pt] [\rightharpoondownfill]
\definemathoverarrow [overrightharpoonup] [\rightharpoonupfill]
\definemathoverarrow [overleftharpoondown] [1pt] [\leftharpoondownfill
