StrSubrange(s, i [, j])

or

string.sub(s, i [, j])

Returns a substring of the string passed.  The substring starts at i.  If the third argument j is not given, the substring ends at the end of the string.  If the third argument is given, the substring ends at and includes the element j.

> print(StrSubrange("Hello HyperMath user", 7))  // from character 7 until the end

HyperMath user

> print(StrSubrange("Hello HyperMath user", 7, 11)) // from character 7 until and including 11

Hyper

> print(StrSubrange("Hello HyperMath user", -10))  // 10 from the end until the end

rMath user

> print(StrSubrange("Hello HyperMath user", -10, -5)) // 10 from the end until 5 from the end

rMath

This can be useful for finding patterns.  For example:

> a,b = StrFind("Hello HyperMath user", "Hy.*")

> s = string.sub("Hello HyperMath user", a,b+1) // excludes last element

> print(s)

HyperMath user