call function calls a specified function with its arguments. It lets you call a user-defined function indirectly when you know the function arguments. The syntax is:
call-function (function-definition-expression [argument] [,....] )
result = call-function (the function-definition that is the-measurement-for TANK-1, the volume of TANK-1, the level of TANK-1)
the-measurement-for is a relation. You cannot use the call function to directly call system functions, which are G2 functions that do not have function-definition items. You could, however, define a function to call system functions, and then use call function to call that function. Within a normal function call, such as:
2 + combine (x, y) combine is a local name, G2 calls the function definition within that local name.