5.37.2 Boundaries of an interval : left right
left (resp. right) takes as argument an interval.
left (resp. right) returns the left (resp. right) boundary
of this interval.
Note that .. is an infixed operator, therefore:

sommet(1..5) is equal to ’..’ and feuille(1..5)
is equal to (1,5).
 the name of the interval followed by
[0] returns the operator ..
 the name of the interval followed by [1]
(or the left command) returns the left boundary.
 The name of the interval followed by [2]
(or the right command)
returns the right boundary.
Input :
(3..5)[0]
or :
sommet(3..5)
Output :
’..’
Input :
left(3..5)
or :
(3..5)[1]
or :
feuille(3..5)[0]
or :
op(3..5)[0]
Output :
3
Input :
right(3..5)
or :
(2..5)[2]
or :
feuille(3..5)[1]
or :
op(3..5)[1]
Output :
5
Remark
left (resp. right) returns also the left (resp. right) member of an
equation (for example left(2*x+1=x+2) returns 2*x+1).