A pair of functions in isolation form a hook whose monadic case is defined as in:
(= <.) y is equivalent to y = <. y
hence the function h=: =<. compares its argument with its integer part, and therefore provides a test for integers. Hooks occur frequently in most sections.
For example:
cf 3 7 15 1 NB. Approximation to pi 3.14159 cfc 3 7 15 1 NB. Convergents to pi 3 3.14286 3.14151 3.14159 cfc 1 1 1 1 1 1 1 NB. Convergents to golden mean 1 2 1.5 1.66667 1.6 1.625 1.61538 cfc 101ドルx NB. As above in extended precision 1 2 3r2 5r3 8r5 13r8 21r13 34r21 55r34 89r55