draft-wfig5

$\begin{array}{lccl} \text{Identifiers（識別子）} & x & & \\ \text{Expressions（式）} & e & ::= & x\\ & & | & e_0 \enspace e_1\\ & & | & \lambda x . e\\ & & | & \textbf{let} \enspace x = e_0 \enspace \textbf{in} \enspace e_1\\ & & | & \textbf{over} \enspace x :: \sigma \enspace \textbf{in} \enspace e\\ & & | & \textbf{inst} \enspace x :: \sigma = e_0 \enspace \textbf{in} \enspace e_1\\ \text{Type Variables（型変数）} & \alpha & & \\ \text{Type Constructors（型構築子）} & \chi & & \\ \text{Types（型）} & \tau & ::= & (\tau \rightarrow \tau ') \enspace | \enspace \alpha \enspace | \enspace \chi (\tau_1 \cdots \tau_n )\\ \text{Predicated Types（述語付きの型）} & \rho & ::= & (x :: \tau) . \rho \enspace | \enspace \tau\\ \text{Type-schemes（型スキーム）} & \sigma & ::= & \forall \alpha . \sigma \enspace | \enspace \rho \end{array}$