Deferred Expressions and Random Values

Definition of random machine imperfections requires evaluation of expressions containing random functions. These are not evaluated like other expressions before a command begins execution, but sampled as required from the distributions indicated when errors are generated. Such an expression is known as a deferred expression. Its value cannot occur as an operand in another expression.

Example:

ERROR:EALIGN,CLASS=QUADRUPOLE,DX=SIGMA*GAUSS();

All elements in range are assigned independent random displacements sampled from a Gaussian distribution with standard deviation SIGMA. The quantity ERROR->DX must not occur as an operand in another expression.