Forcing a result from verify to return a Boolean value is too restrictive, so a more general class of objects may be returned, with the Boolean value of these being checked by the above types.

A result from a call to verify is considered to be true if the result is true.  A result from a call to verify is considered to be either false or FAIL if either of those values is returned, or if a list containing either false or FAIL as a first operand is returned, respectively.

The special verification boolean will convert all return values which are lists to return the first operand of the list.  This can be used if a boolean value is expected by some procedure.

The special verification truefalse will convert all return values which are lists to return the false.  This can be used if a truefalse value is expected by some procedure.

$\mathrm{type}\left(\mathrm{true}\,'\mathrm{verify}'\left('\mathrm{true}'\right)\right)$

$\mathrm{true}$

$\mathrm{type}\left(\mathrm{false}\,'\mathrm{verify}'\left('\mathrm{false}'\right)\right)$

$\mathrm{true}$

$\mathrm{type}\left(\left[\mathrm{false}\,0.100{10}^8\,'\mathrm{ulps}'\right]\,'\mathrm{verify}'\left('\mathrm{false}'\right)\right)$

$\mathrm{true}$

$\mathrm{verify}\left(10\,10.000001\,\mathrm{float}\left(2\right)\right)$

$\left[\mathrm{false}\,100.\,\mathrm{ulps}\right]$

$\mathrm{verify}\left(10\,10.000001\,\mathrm{boolean}\left(\mathrm{float}\left(2\right)\right)\right)$

$\mathrm{false}$

$\mathrm{verify}\left(x\,\mathrm{\pi }\,\mathrm{greater\_than}\right)$

$\mathrm{FAIL}$

$\mathrm{verify}\left(x\,\mathrm{\pi }\,\mathrm{truefalse}\left(\mathrm{greater\_than}\right)\right)$

$\mathrm{false}$

$\mathrm{select}\left(\mathrm{verify}\,\left[1\,2\,3\,x\right]\,\mathrm{\pi }\,\mathrm{less\_than}\right)$

$\left[1\,2\,3\right]$

$\mathrm{select}\left(\mathrm{verify}\,\left[1\,2\,3\,x\right]\,\mathrm{\pi }\,\mathrm{truefalse}\left(\mathrm{less\_than}\right)\right)$

$\left[1\,2\,3\right]$