gistfile1.scm

(define-syntax nested-loop
  (syntax-rules ()
    ((NESTED-LOOP continuation ((state initial) ...) combiner
         clause0 clause1+ ...)
     (%NESTED-LOOP LOOP continuation ((state initial) ...) combiner
         clause0 clause1+ ...))))

(define-syntax %nested-loop
  (syntax-rules (PARALLEL NESTED DO LET LET-VALUES IF NOT AND OR)

    ((%NESTED-LOOP looper continuation ((state initial) ...) combiner
       expression)
     (LET ((state initial) ...)
       (combiner (LAMBDA () expression) continuation)))

    ((%NESTED-LOOP looper continuation ((state initial) ...) combiner
         (PARALLEL (iterator ...) ...)
         clause0 clause1+ ...)
     (looper CONTINUE ((WITH state initial)
                       ...
                       (iterator ...)
                       ...)
       => (continuation state ...)
       (%NESTED-LOOP looper (LAMBDA (state ...) (CONTINUE state ...))
           ((state state) ...)
           combiner
           clause0 clause1+ ...)))

    ((%NESTED-LOOP looper continuation ((state initial) ...) combiner
         (NESTED clause ...)
         clause0 clause1+ ...)
     (%NESTED-LOOP looper continuation ((state initial) ...) combiner
         clause ... clause0 clause1+ ...))

    ((%NESTED-LOOP looper continuation ((state initial) ...) combiner
         (DO command ...)
         clause0 clause1+ ...)
     (BEGIN command ...
            (%NESTED-LOOP looper continuation ((state initial) ...) combiner
                clause0 clause1+ ...)))

    ((%NESTED-LOOP looper continuation ((state initial) ...) combiner
         (LET ((variable value) ...))
         clause0 clause1+ ...)
     (LET ((variable value) ...)
       (%NESTED-LOOP looper continuation ((state initial) ...) combiner
           clause0 clause1+ ...)))

    ((%NESTED-LOOP looper continuation ((state initial) ...) combiner
         (LET variable value)
         clause0 clause1+ ...)
     (LET ((variable value))
       (%NESTED-LOOP looper continuation ((state initial) ...) combiner
           clause0 clause1+ ...)))

    ((%NESTED-LOOP looper continuation ((state initial) ...) combiner
         (LET-VALUES ((bvl expression) ...))
         clause0 clause1+ ...)
     (LET-VALUES ((bvl expression) ...)
       (%NESTED-LOOP looper continuation ((state initial) ...) combiner
           clause0 clause1+ ...)))

    ((%NESTED-LOOP looper continuation ((state initial) ...) combiner
         (LET-VALUES bvl expression)
         clause0 clause1+ ...)
     (LET-VALUES ((bvl expression))
       (%NESTED-LOOP looper continuation ((state initial) ...) combiner
           clause0 clause1+ ...)))

    ((%NESTED-LOOP looper continuation ((state initial) ...) combiner
         (IF condition)
         clause0 clause1+ ...)
     (IF condition
         (%NESTED-LOOP looper continuation ((state initial) ...) combiner
             clause0 clause1+ ...)
         (continuation initial ...)))

    ((%NESTED-LOOP looper continuation ((state initial) ...) combiner
         ((iterator ...) ...)
         clause0 clause1+ ...)
     (%NESTED-LOOP looper continuation ((state initial) ...) combiner
         (PARALLEL (iterator ...) ...)
         clause0 clause1+ ...))

    ;** This clause must come last!  It would shadow the others.

    ((%NESTED-LOOP looper continuation ((state initial) ...) combiner
         (iterator ...)
         clause0 clause1+ ...)
     (%NESTED-LOOP looper continuation ((state initial) ...) combiner
         (PARALLEL (iterator ...))
         clause0 clause1+ ...))))