C/in keyword

element C container

evaluates to true/1B if

element

is contained in the

container

.

element !C container

evaluates to true/1B if

element

is not contained in the

container

.

You can shorten condition

a == b | a == c

using

C

/

in

this way:

a C (b, c)

Also note that this code:

I source[i] C ‘a’..‘z’ | source[i] C ‘A’..‘Z’ | source[i] C ‘0’..‘9’ | source[i] == ‘_’
   ...

can be shortened to:

I source[i] C (‘a’..‘z’, ‘A’..‘Z’, ‘0’..‘9’, ‘_’)
   ...