Algol 68 - ACM Digital Library

84 van Wijngaarden, et al.b) row ROWS leaving ROWSETYI ROWSETY2 NEST indexer{a,b} :row leaving ROWSETYI NEST indexer{c,d,-}, and also{94f] token,ROWS leaving ROWSETY2 NEST indexer{b,c,d,-}.c) row leaving EMPTY NEST indexer{a,b} : NEST subscript{e}.d) row leaving row NEST indexer{a,b} : NEST trimmer{f} ;NEST revised lower bound{g} option.e) NEST subscript[e} : meek integral NEST unit{32d}.f) NEST trimmer{d} : NEST lower bound{46m} option, up to{94f} token,NEST upper bound{46n} option,NEST revised lower bound{g} option.g) NEST revised lower bound{d,f} :at{94f} token, NEST lower bound{46m}.h) * trimscript : NEST subscript{e} ; NEST trimmer{f} ;NEST revised lower bound{g} option.i) *indexer : ROWS leaving ROWSETY NEST indexer{b,c,d}.j) *boundscript : NEST subscript{e} ; NEST lower bound{46m} ;NEST upper bound{46n} ; NEST revised lower bound{g}.{Examples:a) x2 [i,j] • x2 [,j]b) 1: 2, j (in x2 [1 : 2,j]) • i, j (in x2 [i,j])c) j (in x2 [1 : 2,j]) d) 1 : 2 • @0 (in xl [@0])e) j f) 1:2 @0g) @0 }{A subscript decreases the number of dimensions by one, but atrimmer leaves it unchanged. In rule a, 'ROWSI" reflects the number oftrimsripts in the slice, and "ROWS2' the number of these which aretrimmers or revised-lower-bound-options.If the value to be sliced is a name, then the yield of the slice is also aname. Moreover, if the mode of the former name is 'reference to flexibleROWSI of MODE', then that yield is a transient name (see 2.1.3.6.c).}5.3.2.2. Semanticsa) The yield W of a slice S is determined as follows:• let Y and 01 ..... I n) be the [collateral} yields of the PRIMARY of Sand of the indexer {b} of S;• it is required that V {if it is a name} be not nil;• let ((r 1, s 1) ..... fin' Sn)) be the descriptor of V or of the value referredto by V;For i = 1 ..... n,Case A: I. is an integer:!• it is required that r.