The IsVowel(s) command tests whether every character in its argument s is an English language vowel.

The vowels are, by definition, the ten characters $''a''$, $''e''$, $''i''$, $''o''$, $''u''$, $''A''$, $''E''$, $''I''$, $''O''$ and $''U''$. No other character is a vowel. In particular, the characters $''y''$ and $''Y''$ are not considered to be vowels for this test.

If every character of the string s is a vowel character, then the value true is returned. Otherwise, the value false is returned. For the empty string, the tested condition is vacuously true.

All of the StringTools package commands treat strings as (null-terminated) sequences of $8$-bit (ASCII) characters.  Thus, there is no support for multibyte character encodings, such as unicode encodings.

The StringTools[IsVowel] command is thread-safe as of Maple 15.

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

$\mathrm{with}\left(\mathrm{StringTools}\right)\:$

$\mathrm{IsVowel}\left(''E''\right)$

$\mathrm{true}$

$\mathrm{IsVowel}\left(''T''\right)$

$\mathrm{false}$

$\mathrm{seq}\left(\mathrm{IsVowel}\left(\mathrm{ch}\right)\,\mathrm{ch}=''aeiouAEIOU''\right)$

$\mathrm{true},\mathrm{true},\mathrm{true},\mathrm{true},\mathrm{true},\mathrm{true},\mathrm{true},\mathrm{true},\mathrm{true},\mathrm{true}$

$\mathrm{IsVowel}\left(''eye''\right)$

$\mathrm{false}$

s := Iota( 1 .. 255 ): # all characters legal in a Maple string

$\mathrm{length}\left(s\right)$

$255$

$\mathrm{Select}\left(\mathrm{IsVowel}\,s\right)$

$''AEIOUaeiou''$

$\mathrm{IsConsonant}≔s\mapsto \mathrm{IsAlpha}\left(s\right)\mathbf{and}\mathbf{not}\mathrm{IsVowel}\left(s\right)$

$\mathrm{IsConsonant}≔s\mapsto \mathrm{StringTools}:-\mathrm{IsAlpha}\left(s\right)\mathbf{and}\mathbf{not}\mathrm{StringTools}:-\mathrm{IsVowel}\left(s\right)$

Remove( IsConsonant, Iota( "a" .. "z" ) );

$''aeiou''$