Symbol >> precedence

"Answer the receiver's precedence, assuming it is a valid Smalltalk

message selector or 0 otherwise.  The numbers are 1 for unary,

2 for binary and 3 for keyword selectors."

self size = 0 ifTrue: [^ 0].

(self first isLetter or: [ self first = $_ ]) ifFalse: [^ 2].

self last = $: ifTrue: [^ 3].

^ 1

#'_foo' precedence.

"1"

#'_+' precedence.

"1"

#'+' precedence. 

"2"

#'foo' precedence.

"1"

#'foo:' precedence.

  "3"

#'_foo:' precedence. 

���3"

And I wonder why we are concerned with _

S.