6.8 Delayed Assignments vs. Functions with No Arguments

In ugLangAssign we discussed the difference between immediate and function:with no arguments delayed assignments. In this section we show the difference between delayed assignments and functions of no arguments.

A function of no arguments is sometimes called a nullary function.

sin24() == sin(24.0)

_{Type: Void}

You must use the parentheses () to evaluate it. Like a delayed assignment, the right-hand-side of a function evaluation is not evaluated until the left-hand-side is used.

sin24()

Compiling function sin24 with type () -> Float

\[\]

-0.90557836200662384514

_{Type: Float}

If you omit the parentheses, you just get the function definition.

sin24

\[\]

sin24()==sin(24.0)

_{Type: FunctionCalled sin24}

You do not use the parentheses () in a delayed assignment...

cos24 == cos(24.0)

_{Type: Void}

nor in the evaluation.

cos24

Compiling body of rule cos24 to compute value of type Float

\[\]

0.42417900733699697594

_{Type: Float}

The only syntactic difference between delayed assignments and nullary functions is that you use () in the latter case.