#OCaml@p : A debugging print system for OCaml

OCaml@p is a tool supporting debug in OCaml programming. When you compile a program by this tool, this tool generates definition of print function automatically, and inserts function calls to print expression attached marker [@p] automatically.

note : This tool doesn't consider use in combination with other PPX tools using attributes.

#How to use

##installationVersion : 1.1.0

required OCaml version : OCaml 4.03.0

OPAM released

install

opam install ocaml_at_p

uninstall

opam remove ocaml_at_p

##How to compile with OCaml@p

When you compile a.ml with OCaml@p

ocamlfind ocamlc(ocamlopt) -package ocaml_at_p -linkpkg a.ml

##How to write code

###Marker for print

In OCaml@p, when you write marker [@p] behind expression that you want to print the return value, so you can print. The marker [@p] is attribute syntax in OCaml.

let add x y = x + y [@p x] [@p y] [@p] [@p _this+100]let a = add 1 10let b [@p] = a

Then，markers ([@p x],[@p y],[@p]) are attached the expression (x + y)．Two marker[@p x] and[@p y] are used to print values of expressionsx andy ，and the marker[@p] is the value of the expressionx + y．The variable_this is specific one bound by result of evaluation to expression (x + y)._this is the special variable bound by the result value of evaluating the expression. The following is result of run the program.

1 <- at [@p x]10<- at [@p y]11<- at [@p]111         <- at [@p _this+100]b = 11      <- at "let b [@p] = a"

###Marker types

There are two types marker[@p],[@ps],let x [@p].

• e [@p] - newline after printing e

• e [@p expr] - newline after printing expr

• e [@ps] - not newline after printing e

• e [@ps expr] - not newline after printing expr

• let x [@p] = e - newline after printting "x = " and e

###Outer module check [@@@ppopen]

This tool cannot be sure to define print function that print a value of datatype defined in other ml files, so it is difficulty for users to understand error messages. Then, users need to write[@@@ppopen module_name] in Toplevel of ml file written markers to be clear that the ml files of module are compiled by OCaml@p.

##limitation

###module from functor(TODO)A program using module generated by functor connot be compiled with OCaml@p. OCaml@p change signature, and functor's arguments signature is also changed. So it cause type error.

###polymorphic valueOCaml@p cannot print polymorphic values e.g. internal a polymorphic function. For example, the marker[@p xs] in the functionlength cannot print.

let rec length = function   | [] -> 0   | x::xs -> 1 + length xs [@p xs]