RND doesn't accept brackets (*solved*)

[programandala.net]

I've just realized RND() is not accepted ("Unexpected token '(' <LP>"), but only RND. I know it doesn't have parameters in Sinclair BASIC, but it's a function anyway. In fact, both INKEY and INKEY() are accepted, and the case is analogous.

I took a look at the functions list of the original ZX Spectrum manual (page 198, Spanish edition), and realized that PI is there! I never thougth it was a function, but a constant. Well, I tried PI() in ZX BASIC and it's not accepted, not a surprise.

It's clear PI is a constant (that's the description in the wiki), but what's the difference between RND and INKEY? They both are functions that need no parameter. I think RND() should be accepted, if only for syntax coherence.

(I've just read the FreeBASIC's RND syntax. It's accepted without brackets, but can have an optional parameter, the seed.)