We take Church’s original syntax:
<Expression> ::= <ident> | (<Expression><Expression>) | (λ<ident><Expression>)and augment it to include Arabic numerals:
<Expression> ::= <ident> | (<Expression><Expression>) | (λ<ident><Expression>) | <digs> <digs> ::= <dig> | <digs> <dig>See an available alternate syntax much like Church used and more commonly used among later workers.
We refer to the (<Expression><Expression>) alternative as an appl.
We exploit utf-8’s ample supply of letters and for just now say that any single latin letter or one of the 1100 some characters of the Yi syllabary is a valid <ident>. I don’t want to depend on some external changing definition of what code-points denote some notion of ‘letter’. The predicate let (in c1.c or c2.c) controls acceptance as <ident>. ((λꈤꈤ)48) -> 48) <dig> is one of the 10 digits 0x30 thru 0x39. Scheme style comments are allowed, consisting of a semicolon up to the next new-line. Spaces, new-lines and comments can be inserted anywhere but in numerals without changing the program meaning.
Church uses capital latin letters to denote valid expressions in his informal discussions of formal expressions. We may need a similar convention for a ‘define’ like scheme. We may also want some some form of expression that includes contents from another named file.
On the Mac Greek, Yi and many other characters and may be entered by cut and paste, or by using the ‘Character Palette’ accessible via
Apple Menu > System Preferences ... > International > Input Menu > check ‘Character Palette’