UML14 — OCL: Let-expressions

his nice feature provides a useful shortcut for writing complex OCL
expressions. However, it is under-defined both syntactically and
semantically.

Syntactically, why stop at one level, as specified by the grammar
rule:

expression := letExpression?
logicalExpression

To make the language more orthogonal, that rule should be
replaced with:

expression := ( letExpression expression )

which, by the way, ensures the correct precedence and evaluation
order. The generic form of the let expression is:

let <variable> = <expression-1> in <expression-2>

what is not so self-evident, is the following: this fancy syntax
somehow hides the fact that semantically this is equivalent to the
lambda-expressions known from functional analysis:

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