Gdtyjr

I am trying to typeset a integer interval like this: [0..m-1]

However, the space between 0,., and m - 1 are too small. Is there a package to improve this?

Let's see how I can make a command that is like a dots but with two dots. Firstly, I use the wisdom of TeX.SE and find how to find the content of a standard definition; then a bit of command line:

[romano:~] % texdef -t latex dots 
dots:
macro:->protect dots 
dots :
long macro:->ifmmode mathellipsis else textellipsis fi 

[romano:~] % texdef -t latex mathellipsis
mathellipsis:
macro:->mathinner ldotp ldotp ldotp 

and finally:

 newcommandtwodotsmathinner ldotp ldotp

which results in:

(This is just for math mode, but you can easily extend it for text too, mimicking the dots definition)

I like the two dots, too. My usual code is

[amathrel.,.nobreak b]

of course hidden in a macro.

documentclassarticle
usepackageamsmath

newcommandisepmathrel.,.nobreak

begindocument

$[0isep m-1]$

enddocument

A more elaborate solution for coping with intervals of any kind, while keeping a syntax that doesn't force a choice.

documentclassarticle
usepackageamsmath,mleftright
usepackagexparse

ExplSyntaxOn
NewDocumentCommandintervalO>SplitArgument1,m
 
 group_begin:
 keys_set:nn calcolo/interval o, #1 
 bool_if:NTF l_calcolo_interval_auto_bool 
 mleftl_calcolo_interval_left_tl
 mathopenl_calcolo_interval_size_tll_calcolo_interval_left_tl
 calcolo_interval_set:nn #2
 bool_if:NTF l_calcolo_interval_auto_bool 
 mrightl_calcolo_interval_right_tl
 mathclosel_calcolo_interval_size_tll_calcolo_interval_right_tl
 group_end:
 
cs_new_protected:Nn calcolo_interval_set:nn
 
 #1 mathrel.,.nobreak #2
 
keys_define:nn calcolo/interval 
 
 size .code:n =
 tl_if_eq:nnTF #1 * 
 bool_set_true:N l_calcolo_interval_auto_bool 
 tl_set:Nn l_calcolo_interval_size_tl #1 ,
 o .code:n =
 tl_set:Nn l_calcolo_interval_left_tl ( 
 tl_set:Nn l_calcolo_interval_right_tl ) ,
 oo .code:n =
 tl_set:Nn l_calcolo_interval_left_tl ( 
 tl_set:Nn l_calcolo_interval_right_tl ) ,
 c .code:n =
 tl_set:Nn l_calcolo_interval_left_tl [ 
 tl_set:Nn l_calcolo_interval_right_tl ] ,
 cc .code:n =
 tl_set:Nn l_calcolo_interval_left_tl [ 
 tl_set:Nn l_calcolo_interval_right_tl ] ,
 oc .code:n =
 tl_set:Nn l_calcolo_interval_left_tl ( 
 tl_set:Nn l_calcolo_interval_right_tl ] ,
 co .code:n =
 tl_set:Nn l_calcolo_interval_left_tl [ 
 tl_set:Nn l_calcolo_interval_right_tl ) ,
 o .value_forbidden:n = true,
 oo .value_forbidden:n = true,
 c .value_forbidden:n = true,
 cc .value_forbidden:n = true,
 oc .value_forbidden:n = true,
 co .value_forbidden:n = true,
 

tl_new:N l_calcolo_interval_left_tl
tl_new:N l_calcolo_interval_right_tl
tl_new:N l_calcolo_interval_size_tl
bool_new:N l_calcolo_interval_auto_bool
ExplSyntaxOff


begindocument

$intervala,b$

$interval[c]a,b$

$interval[co]a,b$

$interval[oc]a,b$

$interval[size=Big]a,b$

bigskip

$interval[size=*,co]dfracdfrac12dfrac34,b$

enddocument

Here is a solution with mathtools and xparse. I define a command Iintvlm,n. You need a font which contains the relevant delimiters, llbracket and rrbracket (fourier and stmaryrd) or equivalents (MnSymbol and MdSymbol have lsem and rsem). The star version of the command adapts the size of the delimiters to the contents, and you can fine-tune their size with an optional argument (big, Big, …).

documentclassarticle
usepackagemathtools, stmaryrd
usepackagexparse DeclarePairedDelimiterXIintv[1]llbracketrrbracketiintvargs#1
NewDocumentCommandiintvargs>SplitArgument1,m
iintvargsaux#1 %
NewDocumentCommandiintvargsauxmm #1mkern1.5mu..mkern1.5mu#2

begindocument

[ Iintv-2,5 quad Iintv*2^n, 2^n + 1 quad Iintv*2^2^n + 1, 2^2^n + 1 + 1]

enddocument 

Much less robust than others (it can of course be made more robust, but may be this is enough), but it might be nice looking and readable code

defintv#1[#2..#3]mathopen#1[#2mathrel.,.nobreak#3mathclose#1]
$
intv[a..b]
intvbig[a..b]
intvBigg[fracab..c]
$

If you need left[ .. right] I can add the code.

Use enleadertwodots in the stix package is perfect (aside from tiny spacing). I've added a couple variations on spacing so you can see how it looks:

documentclass[10pt]article
usepackagestix
begindocument

[[1, enleadertwodots, m-1] quad [1 enleadertwodots, m-1] quad [1 enleadertwodots m-1]]

enddocument

I found this after scanning through this huge list of symbols in latex.