# KnotInfo: Search Help

A simplest form of a search criterion consists of a field name, a
comparison operator, and a value. For example, if you like to generate a
table of knots with signature less than or equal to 4, the following search
criterion may be used:

` signature <= 4 `

Each field in the knot table is represented by a field name such as
`signature` and `bridge_index`.
An easier way to input a field name is to use "Field Name Input Helper"
dropdown box beside the search criterion input area. Choosing a
description of a field from the dropdown box, the associated field name is
appended to the end of the current contents of the search criterion box.
Once you remember frequently used field names, you can type in them
directly.

Comparison operators includes `=`, `!=`, `<`,
`<=`, `=>`, `>`.

Elementary expressions can be combined using logical operators
`and`, `or` together with parentheses. For example,

` signature = 0 and khovanov_s_invariant != 0 `

` braid_index > 3 and symmetry_type = "negative amphicheiral" `

will find knots whose signature is trivial but the s-invariant of Rasmussen
is nontrivial.

Tools for searching non-numerical data are not fully implemented yet. These should be searched using the exact format of the data as it appears in tables. Thus, as in the example above, one can search such things as ` symmetry_type = "reversible" and alexander_polynomial = "2*t^2-3*t+2 or alexander_polynomial = "-2*t^2+3*t-2"``.
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