Add contracts related to nutrient-value.

1 files changed, 5 insertions, 1 deletions

diff --git a/models/nutrient.rkt b/models/nutrient.rkt
index dd8d677..1103aac 100644
--- a/models/nutrient.rkt
+++ b/models/nutrient.rkt
@@ -6,6 +6,8 @@
          nutrient-canonical-name
          nutrient-french-name
          nutrient-formula
+         nutrient-value?
+         maybe-nutrient-value?
          nutrient-value-hash/c
          (contract-out [create-nutrient! (-> string? string? string? nutrient?)]
                        [get-nutrients (-> (listof nutrient?))]
@@ -33,7 +35,9 @@
   #:property prop:custom-write
   (λ (v out _) (fprintf out "#<~a ~a>" (nutrient-id v) (nutrient-canonical-name v))))
 
-(define nutrient-value-hash/c (hash/c nutrient? (and/c real? (>=/c 0)) #:immutable #t))
+(define nutrient-value? (and/c real? (>=/c 0)))
+(define maybe-nutrient-value? (or/c nutrient-value? #f))
+(define nutrient-value-hash/c (hash/c nutrient? nutrient-value? #:immutable #t))
 
 ;; vector/c id, canonical name, french name, nutrient formula, value (ppm)
 (define residual-vector/c (vector/c exact-nonnegative-integer? string? string? string? real?))