Circular shifting

The operations on texts HEAD and TAIL that are available in Elan-0 differ markedly from the standard operations in the language, being much more list-oriented. In standard Elan they can be programmed as

$\begin{elan} TEXT OP HEAD ( TEXT CONST a ) : a SUB 1 ENDOP HEAD ; \par TEXT OP TAIL ( TEXT CONST a ) : subtext ( 2 , LENGTH a , a ) ENDOP TAIL ; \end{elan}$

The following program repeatedly rotates its input text by one position until the original is obtained again.

$\begin{elan} rotate : declare texts ; REP shift s circularly ; display ... ...t ( s ) . \par shift s circularly : s := ( TAIL s ) + ( HEAD s ) . \end{elan}$