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The substring function extracts a substring from a string or symbol . By default, if applied to a string, a string is returned. If applied to a symbol, a symbol is returned.

If a range is specified for range, and m and n evaluate to integers then substring extracts a substring from string starting with the mth character and ending with the nth character.

Specifying a single integer m for range is equivalent to specifying the range m..m.

Negative values for m and/or n stand for positions counted leftwards from the right end of the string. The range 1..-1 refers to the entire string. The range -20..-1 refers to the last 20 characters of the string.

If n is greater than the length of string then substring returns a string from the mth character to the end of string. If m is equal to n + 1 then substring returns the null string.

If m is greater than the length of string then substring returns the null string.

Zero values for m and/or n are not permitted, except for the case m = 1 and n = 0, which returns the null string as described above.

If either m or n fails to evaluate to an integer, then substring remains unevaluated.

The optional type argument specifies the type of value returned by substring. If type is one of the symbols symbol or name, then a symbol is always returned, even if the first argument is a string. If type is string, then a string is always returned, even if the first argument is a symbol.

The substring command is thread-safe as of Maple 15.

For more information on thread safety, see index/threadsafe .

$\mathrm{substring}\left(\mathrm{abcdefgh}\,3..7\right)$

$\mathrm{cdefg}$

$\mathrm{substring}\left(\mathrm{abcdefgh}\,5\right)$

$e$

$\mathrm{substring}\left(''abcdefgh''\,-5..-1\right)$

$''defgh''$

$\mathrm{substring}\left(\mathrm{wxyz}\,2..2\right)$

$x$

$\mathrm{substring}\left(''abcdefgh''\,2..4\,\mathrm{symbol}\right)$

$\mathrm{bcd}$

$\mathrm{substring}\left(\mathrm{wxyz}\,2..3\,\mathrm{string}\right)$

$''xy''$