{not available when compiled without the |+cindent| or |+eval| features} Expression which is evaluated to obtain the proper indent for a line. It is used when a new line is created, for the |=| operator and in Insert mode as specified with the 'indentkeys' option. When this option is not empty, it overrules the 'cindent' and 'smartindent' indenting. When 'lisp' is set, this option is overridden by the Lisp indentation algorithm. When 'paste' is set this option is not used for indenting. The expression is evaluated with |v:lnum| set to the line number for which the indent is to be computed. The cursor is also in this line when the expression is evaluated (but it may be moved around). The expression must return the number of spaces worth of indent. It can return "-1" to keep the current indent (this means 'autoindent' is used for the indent). Functions useful for computing the indent are |indent()|, |cindent()| and |lispindent()|. The evaluation of the expression must not have side effects! It must not change the text, jump to another window, etc. Afterwards the cursor position is always restored, thus the cursor may be moved. Normally this option would be set to call a function: > :set indentexpr=GetMyIndent() < Error messages will be suppressed, unless the 'debug' option contains "msg". See |indent-expression|. NOTE: This option is set to "" when 'compatible' is set.