Uploaded at Mar 4 16:36:50 2021
Succesfully tested at Mar 7 06:47:15 2021

Curry Package curry-repl


This package contains the implementation of a universal REPL (Read-Eval-Print-Loop) which can be used on top of a Curry compiler. Thus, if the Curry compiler supports some standard options (see below), it can be extended to a simple interactive programming environment.

The specification of the concrete compiler is provided as an element of type REPL.Compiler.CCDescription. The entry point of the REPL is the operation mainREPL defined in module REPL.Main. The directory examples contains example specifications.

Requirements for a Curry Compiler used by a REPL

Basically, the REPL translates each expression to be evaluated into a program with a main operation. This program is compiled and then executed. In order to implement this kind of REPL, it should be possible to invoke the Curry compiler cc as follows:

cc [-vn] [-iDIR] ... [-iDIR] [--parse-options="PO"] [-c|--compile] MOD
  • -vn: verbosity with 0<=n<=4
  • -iDIR: use DIR to search for imported modules
  • -c: compile only
  • PO: options passed to the Curry front end
  • MOD: the module to be compiled containing an operation main

This command should compile module MOD (and, if necessary, all imported modules) and create an executable MOD which executes the operation main in this module. MOD might be a hierarchical module name, e.g., Dir.Mod. In this case, the executable Dir.Mod is generated where the source code of the module is stored in Dir/Mod.curry.

If the option -c or --compile is provided, the executable is not generated. This might be reasonable to compile all modules in order to check for errors and speed up later compilations without re-compiling all imports.

If the module name is prefixed by a path, e.g., dir1/dir2/Mod, then we change into the directory of the path (dir1/dir2) and compile the main module there.

Further options:

Options beyond this general usage might depend on the compiler. For instance, each compiler might implement a different set of search strategies. Here are some examples of options and their values:

  • interactive (yes/no): should the user be asked to print the next result?
  • first (yes/no): print only one result and stop?
  • results (int n): number of results to be printed (n=0: infinite)
  • time (yes/no): print execution time?
  • strategy: search strategy to be used, e.g., dfs/bfs/ids/fs
  • debug (yes/no): interactive debugging
  • trace (yes/no): trace evaluation
  • printdepth (int d): print resulting terms up to depth d (d=0: no limit)

The actual options are specified by data of type CCOption (see module REPL.Compiler).

Requirements for Curry Compilers used by CPM

In order to use a Curry compiler together with CPM, it has to support some options so that CPM can interact with the compiler. The Curry REPL implements these options provided that the Curry compiler itself provides options about its version. If cc is the executable of the compiler, the following options must exist:

  • cc --compiler-name: Shows that name of the compiler (which occurs in compiler dependencies of package specifications) and quits.
  • cc --numeric-version: Shows the compiler version quits.
  • cc --base-version: Shows the version of the base libraries implemented by the compiler and quits.

These options can also be combined. In this case the information is shown in subsequent lines, as shown in this example for PAKCS:

> pakcs --compiler-name --numeric-version --base-version

The intermediate files produced by the compiler should be stored in the directory


relative to the directory of the source file. If the source file is a hierarchical module, the same hierarchy is used relative to .curry.

Running programs

When CPM starts a Curry system (via cypm curry), it sets the environment variable CURRYPATH to the load path of all included packages and passes the option --nocypm to the executable of the Curry system. Usually, when a Curry system is started, it should query CPM (by cypm deps -p) to get the value of CURRYPATH to load modules. The option --nocypm is intended to turn off this behavior.

Installing executables

If CPM installs an executable, it passes the following options (REPL commands) to the compiler:

> cc :set v0 :load MAINMOD :save :quit

(where v0 is replaced by v1 in debug mode). The execution of this command should install the executable MAINMOD.


Checkout with CPM:
cypm checkout curry-repl 0.0.1
Package source:
curry-repl-0.0.1.tar.gz [browse]
Source repository: