(math-standard-units): Give exact conversion for tsp.

diff --git a/lisp/calc/calc-units.el b/lisp/calc/calc-units.el
index ae94fc43ae1efdf7a42bc0c559f4416be11daafa..3724490169a6a3fce471aa674d373157622a377e 100644 (file)
--- a/lisp/calc/calc-units.el
+++ b/lisp/calc/calc-units.el
@@ -89,7 +89,9 @@
     ( ozfl    "2 tbsp"               "Fluid Ounce" )
     ( floz    "2 tbsp"               "Fluid Ounce" )
     ( tbsp    "3 tsp"                "Tablespoon" )
-    ( tsp     "4.92892159373 ml"     "Teaspoon" ) ;; (approx) ESUWM
+    ;; ESUWM defines a US gallon as 231 in^3.
+    ;; That gives the following exact value for tsp.
+    ( tsp     "492892159375*10^(-11) ml" "Teaspoon" ) 
     ( vol     "tsp+tbsp+ozfl+cup+pt+qt+gal" "Gallons + ... + teaspoons" )
     ( galC    "galUK"                "Canadian Gallon" )
     ( galUK   "454609*10^(-5) L"     "UK Gallon" ) ;; NIST