In Sets, bags, and mixes§

See primary documentation in context for infix (<), infix ⊂.

Returns True if $a is a strict subset of $b, else False. More information, Wikipedia definition.

In Operators§

See primary documentation in context for infix (<), infix ⊂.

multi infix:«(<)»($a,$b --> Bool:D)

Subset of operator.

Returns True if $a is a strict subset of $b, i.e., that all the elements of $a are elements of $b but $a is a smaller set than $b.

say (1,2,3) (<) (2,3,1); # OUTPUT: «False␤»
say (2,3) (<) (2,3,1);   # OUTPUT: «True␤»
say 4  (1,2,3);         # OUTPUT: «False␤»