From my recitation class -
Can you please explain
why does operator $"+"$ signature is $ int \rightarrow (int \rightarrow int)$ ?
How does this graph is build ?
And what is mean $t=u \rightarrow s$ ?
Thanks in advance .
ML functions take a single argument. There are two common techniques to pass two arguments to a function.
The graph, and the derivation on the left, present a simple approach to ML type inference by unification. The first steps are with the atomic subexpressions:
The graph represents the unification steps (with some trivial steps for atomic subexpressions omitted). Four variables $r$, $s$, $t$, $u$ are created to designate the type of each of the non-atomic subexpressions. The straight lines show the expression tree. The curvy line links the occurrence of the variable $x$ with its binding site.