draft: specify numerical functions

specgen/spec/sec-gates.s

@@ -332,7 +332,7 @@ DEFGATE TT p q AS SEQUENCE:
     T p
     T q
 }
-@p{The standard gate `CSWAP` (Toffoli) could be defined with the following definition:}
+@p{The standard gate @c{CSWAP} (Toffoli) could be defined with the following definition:}
 @clist{
 DEFGATE TOFFOLI p q r AS SEQUENCE:
     H        r
@@ -343,7 +343,7 @@ DEFGATE TOFFOLI p q r AS SEQUENCE:
     CNOT     q r
     DAGGER T r
     CNOT     p r
-    #Note the use of TT here
+    # Note the use of TT here
     TT       q r
     CNOT     p q
     H        r
@@ -353,8 +353,7 @@ DEFGATE TOFFOLI p q r AS SEQUENCE:
 }
 @p{An arbitrary Euler rotation could be expressed as:}
 
-@clist{    
-
+@clist{
 DEFGATE EULER(%alpha, %beta, %gamma) p AS SEQUENCE:
     RY(%alpha) p
     RZ(%beta)  p 

specgen/spec/sec-structure.s

@@ -206,7 +206,7 @@ associativity directions.
 
 @syntax[:name "Term"]{
          - @ms{Expression}
-    @alt @ms{Identifier} ( @ms{Expression} )
+    @alt @ms{Function Expression}
     @alt ( @ms{Expression} )
     @alt @ms{Complex}
     @alt @ms{Parameter}
@@ -230,6 +230,28 @@ enough to warrant their own production.}
     }
 }
 
+@p{This allows us to specify the @ms{Function Expression}.}
+
+@syntax[:name "Function Expression"]{
+        @ms{Function Name} ( @ms{Expression List} )
+}
+
+
+@subsubsection[:title "Functions in Arithmetic Expressions"]
+
+@p{The following functions are allowed to be used in function
+expressions.}
+
+@syntax[:name "Function Name"]{
+         @ms{Trigonometric Function Name}
+    @alt @ms{Inverse Trigonometric Function Name}
+    @alt @ms{Algebraic Function Name}
+    SIN | COS | TAN | ASIN | ACOS | ATAN | SQRT | ATAN2
+}
+
+@p{All functions listed take on their usual definitions over the
+complex numbers.}
+
 @subsection[:title "Main Program Elements"]
 
 @p{A Quil program consists of declarations, directives, and