The assignment is a unit of the form
where <#1628#>var<#1628#> is a variable of some type and <#1629#>expr<#1629#> an
expression of the same type.
The assignment serves to change the value of the variable. It
is executed by first executing the expression and then making
its value the new value of the variable. The value of all other
variables remains unchanged.
Thus the assignment
which can be read as ``x becomes x plus one'' does not mean that
in some curious way <#1632#>x<#1632#> becomes equal to itself plus one,
but rather that first the sum of the present value of <#1633#>x<#1633#>
and one is computed and then that value is made to be the new
value of <#1634#>x<#1634#>.