Module 03 & 04 Cards

Front 1

Immutable

Back 1

ML Syntax dictates that we cannot change the value of 'x' to something else later on. We can shadow it, or even use an alias; but it remains Immutable.

Front 2

Function Binding

Back 2

Syntax: fun x0 (x1 : t1, x2 : t2..., xn : tn)

Type-Checking: maps x1 to t1, x2 to t2, ... resulting in type x0

Evaluation: add x0 to the envoirnment as a function that can be called later.

Front 3

Recursive

Back 3

The ability to 'work backwards' i.e. using the head or tail of a list, then coming back through from tail to head.

Front 4

Type Inference

Back 4

Syntax:

Type Checking:

Evaluation:

Front 5

Function Calls

Back 5

Syntax: fun <identifier> (<parameter list>) = <expression>;
e.g. fun square( x) = x * x;

Type Checking: Function calls are typechecked in the obvious way: the actual argument must match the formal argument type. When it does not, you get an error.

Evaluation:

* The return value is the entire body of the function. Since ML proceeds by evaluaton of expressions, this is a natural way to define functions: the body is an expression that gets evaluated. This design differs from imperative languages, where a function body is usually a block of code to be executed.