General form:

par('expression')
output=par('expression')  $ not in .measure ac

Examples:

.four 1001 sq1=par('v(1)*v(1)')
.measure tran vtest find par('(v(2)*v(1))') AT=2.3m
.print tran output=par('v(1)/v(2)') v(1) v(2)
.plot dc v(1) diff=par('(v(4)-v(2))/0.01') out222

With the output lines .four, .plot, .print, .save and in .measure evaluation it is possible to add algebraic expressions for output, in addition to vectors. All of these output lines accept par**('expression')**, where expression is any expression valid for a B source (see Chapt. 5.1). Thus expression may contain predefined functions, numerical values, constants, simulator output like v(n1) or i(vdb), parameters predefined by a .param statement, and the variables hertz, temper, and time. Note that a B-source, and therefore the par('...') feature, operates on values of type complex in AC analysis mode.

Internally the expression is replaced by a generated voltage node that is the output of a B source, one node, and the B source implementing par**('...')**. Several par('...') are allowed in each line, up to 99 per input file. The internal nodes are named pa_00 to pa_99. An error will occur if the input file contains any of these reserved node names.

In .four, .plot, .print, .save, but not in .measure, an alternative syntax
output**=par('expression') is possible. par('expression') may be used as described above. output is the name of the new node to replace the expression. So output has to be unique and a valid node name.

The syntax of output**=par(expression)** is strict, no spaces between par and (', or between ( and ' are allowed, (' and ') both are required. Also there is not much error checking on your input, if there is a typo, for example, an error may pop up at an unexpected place.