-val evaluate_targets : Ast.env -> Ast.expr list -> unit
-(** This drives evaluation of the list of expressions (in parallel)
- until they are complete or we reach an error. The expressions
- are either a list of dependencies or a list of initial targets. *)
+(** Take any expression and simplify it down to a constant.
+ If the expression cannot be simplified then this raises
+ [Failure _]. *)
+val to_constant : Ast.env -> Ast.expr -> Ast.constant
+
+(** Take a substitution list and try to turn it into a simple
+ string by evaluating every variable. If not possible this
+ raises [Failure _]. *)
+val substitute : Ast.env -> Ast.loc -> Ast.substs -> string
+
+(** Similar to {!substitute} except this is used where we will
+ pass the result immediately to the shell to execute. Variables
+ are substituted with shell quoted strings. Raises [Failure _]
+ on error. *)
+val to_shell_script : Ast.env -> Ast.loc -> Ast.substs -> string
+
+(** Evaluate a goal argument. This substitutes any variables found,
+ and recursively calls functions. *)
+val evaluate_goal_arg : Ast.env -> Ast.expr -> Ast.expr