Optional parameters: Difference between revisions

=={{header|ALGOL 68}}==▼

<lang algol68># as the options have distinct types (INT, BOOL and PROC( STRING, STRING )INT) the #▼

# easiest way to support these optional parameters in Algol 68 would be to have an array #▼

# with elements of these types #▼

# See the Named Arguments sample for cases where the option types are not distinct #▼

# default comparison function #▼

PROC default compare = ( STRING a, b )INT: IF a < b THEN -1 ELIF a = b THEN 0 ELSE 1 FI;▼

# sorting procedure #▼

PROC configurable sort = ( [,]STRING data, []UNION( INT, BOOL, PROC( STRING, STRING )INT ) options )VOID:▼

BEGIN▼

# set initial values for the options #▼

INT sort column := 2 LWB data;▼

BOOL reverse sort := FALSE;▼

PROC( STRING, STRING )INT comparator := default compare;▼

# overide from the supplied options #▼

FOR opt pos FROM LWB options TO UPB options DO▼

CASE options[ opt pos ]▼

IN ( PROC( STRING, STRING )INT p ): comparator := p▼

, ( INT c ): sort column := c▼

, ( BOOL r ): reverse sort := r▼

ESAC▼

OD▼

# do the sort .... #▼

END # configurable sort # ;▼

# example calls #▼

[ 1 : 2, 1 : 3 ]STRING data := ( ( "a", "bb", "cde" ), ( "x", "abcdef", "Q" ) );▼

# sort data, default comparison, first column, reverse order #▼

configurable sort( data, ( TRUE ) );▼

# sort data, second column, ignore first chaacter when sorting, normal order #▼

configurable sort( data, ( 2, ( STRING a, STRING b )INT: default compare( a[ LWB a + 1 : ], b[ LWB b + 1 : ] ) ) );▼

# default sort #▼

configurable sort( data, () )</lang>▼