[expr] function available since [Tcl] 8.5:  '''tcl::matchfunc::entier'''


Converts a number to ''some'' integral type ([int], [wide] or [bignum]).
This function was introduced in [http://tip.tcl.tk/237%|%TIP#237].

The name of this function is derived from French, via ALGOL [http://www.masswerk.at/algol60/modified_report.htm#A2].  It also shows up in Tcl as a subcommand of [string is]
----

This is different from [tcl::mathfunc::int] in that it won't overflow: 

======
% expr int(256**$::tcl_platform(wordSize))
0
% expr entier(256**$::tcl_platform(wordSize))
18446744073709551616
======

***Rounding behaviour***
Note that '''entier''' will truncate the decimal part of a number, effectively 'rounding towards 0':

======
% expr entier(-1.6)
-1
% expr entier(1.6)
1
======

[Lars H]: As a rounding function, this is unfortunately not particularly good. 
There a four common ways to round doubles to integers, three of which 
are useful:
   To nearest integer:   This is [round].
   To smallest integer >= given number:   This has to be coded as `round(ceil($x))`.
   To greatest integer <= given number:   This has to be coded as `round(floor($x))`.
and one which is not:
   Round towards zero:   A.k.a. truncating decimals. This is [entier]. Specified by the hideous inequality 1 > abs($x) - abs(entier($x)) >= 0.

At least one specification of Algol (now linked above) was careful to not allow such behaviour for that entier.

[PL] 2014-12-29: then again, `entier` ''isn't'' a rounding function. Like `[int]` or `[wide]`, it's a ''coercion'' function. If this coercion were combined with rounding, the implementation would in effect be making choices the programmer would like to have some control over.

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