SML# Document Version 3.7.1

19 Expressions 19.15 Exception expression raise

\,\langle

\rangle\,

19.17 While expression while

\,\langle

exp

{}_{1}

\rangle\,

\,\langle

exp

{}_{2}

\rangle\,

19.16 Conditional expression if $\,\langle$ exp ${}_{1}$ $\rangle\,$ then $\,\langle$ exp ${}_{2}$ $\rangle\,$ else $\,\langle$ exp ${}_{3}$ $\rangle\,$

This is for conditional branches. $\,\langle$ exp ${}_{1}$ $\rangle\,$ must be of bool type. The type of $\,\langle$ exp ${}_{2}$ $\rangle\,$ and $\,\langle$ exp ${}_{3}$ $\rangle\,$ must be same. Under these restrictions, this entire expression have the same type as $\,\langle$ exp ${}_{2}$ $\rangle\,$ .

This is evaluated as follows. $\,\langle$ exp ${}_{1}$ $\rangle\,$ is evaluated at first. If its value is true, $\,\langle$ exp ${}_{2}$ $\rangle\,$ is evaluated and the resulting value is the value of the entire expression. Otherwise, $\,\langle$ exp ${}_{3}$ $\rangle\,$ is evaluated and the resulting value is the value of the entire expression.

19.16 Conditional expression if ⟨exp1⟩ then ⟨exp2⟩ else ⟨exp3⟩

19.16 Conditional expression if $\,\langle$ exp ${}_{1}$ $\rangle\,$ then $\,\langle$ exp ${}_{2}$ $\rangle\,$ else $\,\langle$ exp ${}_{3}$ $\rangle\,$