NSF -- Normalized Syntactic Form

1. What NSF is

NSF is the linear, fully disambiguated syntactic representation of a Logo program, immediately prior to structural (AST) construction.

Or: NFS is the last representation of a cLogos program that still reflects how the user wrote it, while already encoding how the reader understood it.

It is:

• syntactic
• local
• disambiguated
• still linear
• still reversible in principle

NSF is the bridge between surface syntax and semantic structure.

2. What NSF is not

NSF is not:

• an AST
• executable
• grouped by precedence
• optimized
• canocicalized beyond local necessity

In particular:

NSF does not impose structure -- it only removes ambiguity.

3. NSF position in the pipeline

The pipeline has a natural stratification:

Source text
  ↓
Tokens (with whitespace, comments, bars)
  ↓
Minus normalisation (local syntactic disambiguation)
  ↓
Infix word decontraction
  ↓
Minus sanity check
  ↓
INFIX replacement
  ↓
-----------------
NSF
-----------------
  ↓
Infix AST construction
  ↓
Procedure AST
  ↓
Compilation

This is the semantic point of no return -- and that is why NSF exists.

4. Core invariants of NSF

These invariants define the contract of the stage.

4.1 Linear order invariant

NSF preserves token order.

• No reordering
• No implicit grouping
• No tree structure

Everything is still a flat sequence inside lines.

4.2 Disambiguation invariant

All syntactic ambiguities that are resolvable without semantic knowledge must already be resolved.

This includes:

• unary vs infix -
• adjacency-sensitive minus
• infix vs procedure words
• decontracted infix expressions (4-3 → 4 - 3)
• generated words are explicitly marked

After NSF:

There is no remaining syntactic ambiguity.

4.3 Explicit operator invariant

Every operator is explicit and typed:

• Infix operators are #S(INFIX ...)
• Unary operators are already #S(PROC ...)
• Variables are WD with :THING flag
• No symbol "+", "-", etc. remains ambiguous

The reader never has to "guess" again.

4.4 Context locality invariant

All decisions made in NSF are:

• local
• context-bounded
• syntax-only

No evaluation, no arity reasoning.

Example:

sum :a - 4

remains unresolved semantically, in this form:

(:DOCUMENT
 ((:LINE
   (#S(PROC
       :NAME "sum"
       :PACKAGE LOGO
       :IMPLEMENTATION #<FUNCTION SUM>
       :DEFAULT-ARITY 2
       :OPTIONAL-ARITY -1
       :VISIBILITY :PUBLIC)
    (:WHITESPACE " ") #S(WD :STR "a" :NMB NIL :SYM NIL :FLAGS (:THING))
    (:WHITESPACE " ")
    #S(INFIX
       :SIGN "-"
       :WEIGHT 60
       :ASSOCIATIVITY :LEFT
       :PROCEDURE #S(PROC
                     :NAME "difference"
                     :PACKAGE LOGO
                     :IMPLEMENTATION #<FUNCTION DIFFERENCE>
                     :DEFAULT-ARITY 2
                     :OPTIONAL-ARITY -1
                     :VISIBILITY :PUBLIC))
    (:WHITESPACE " ") #S(WD :STR "4" :NMB 4 :SYM NIL :FLAGS NIL))
   :LINE-META (:LINE-NO 1)))
 :META
 (:STRUCTURE (:STATUS :BALANCED :DEPTH 0 :ISSUES NIL) :EOF (:STATUS :COMPLETE)))

4.5 Reconstructability invariant (weak)

From NSF, it is still possible to:

• pretty-print a faithful representation
• explain to the user how the input was read
• reason about spacing and style

But:

• exact original text reconstruction is not required, only close to the input
• stylistic loss is acceptable

This is intentional.

5. NSF data model expectations

In NSF:

• Lines are still (:LINE ...)
• Whitespace tokens may still exist
• Comments may still exist
• WD, PROC, INFIX delimiters are all explicit
• Flags like :thing or :quoted are meaningful

AST nodes must not appear.

6. Relationship to GLOSS :SOURCE

GLOSS :SOURCE

• Stores final AST
• Represents what is executed
• Canonical
• Stable

NSF

• Stored optionally (workspace / history /debugging)
• Represents how input was understood
• Pedagogical
• Inspectable
• Disposable