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File: omake-doc, Node: Subsection 3-5-5,	Prev: Subsection 3-5-4,	Up: Section 3-5


3.5.5  Finishing up
===================

  At this point we are done, but there are a few things we can consider.
  First, the rules for building cat programs is defined in the project
OMakefile. If you had another cat project somewhere, you would need to
copy the OMakeroot (and modify it as needed). Instead of that, you
should consider moving the configuration to a shared library directory,
in a file like Cat.om. That way, instead of copying the code, you could
include the shared copy with an OMake command open Cat. The share
directory should be added to your OMAKEPATH environment variable to
ensure that omake knows how to find it.
  Better yet, if you are happy with your work, consider submitting it as
a standard configuration (by sending a request to omake@metaprl.org) so
that others can make use of it too.

File: omake-doc, Node: Section 3-6,	Prev: Section 3-5,	Up: Chapter 3


3.6  Collapsing the hierarchy, .SUBDIRS bodies
**********************************************

   
  Some projects have many subdirectories that all have the same
configuration. For instance, suppose you have a project with many
subdirectories, each containing a set of images that are to be composed
into a web page. Apart from the specific images, the configuration of
each file is the same.
  To make this more concrete, suppose the project has four
subdirectories page1, page2, page3, and page4. Each contains two files
image1.jpg and image2.jpg that are part of a web page generated by a
program genhtml.
  Instead of of defining a OMakefile in each directory, we can define it
as a body to the .SUBDIRS command.
<<    .SUBDIRS: page1 page2 page3 page4
          index.html: image1.jpg image2jpg
              genhtml $+ > $@
>>

  The body of the .SUBDIRS is interpreted exactly as if it were the
OMakefile, and it can contain any of the normal statements. The body is
evaluated in the subdirectory for each of the subdirectories. We can see
this if we add a statement that prints the current directory ($(CWD)).
<<    .SUBDIRS: page1 page2 page3 page4
          println($(absname $(CWD)))
          index.html: image1.jpg image2jpg
              genhtml $+ > $@
    # prints
      /home/jyh/.../page1
      /home/jyh/.../page2
      /home/jyh/.../page3
      /home/jyh/.../page4
>>

* Menu:

* Subsection 3-6-1::	Using glob patterns
* Subsection 3-6-2::	Simplified sub-configurations
* Subsection 3-6-3::	Computing the subdirectory list
* Subsection 3-6-4::	Temporary directories


File: omake-doc, Node: Subsection 3-6-1,	Next: Subsection 3-6-2,	Up: Section 3-6


3.6.1  Using glob patterns
==========================

  Of course, this specification is quite rigid. In practice, it is
likely that each subdirectory will have a different set of images, and
all should be included in the web page. One of the easier solutions is
to use one of the directory-listing functions, like 'glob' or 'ls'. The
glob function takes a shell pattern, and returns an array of file with
matching filenames in the current directory.
<<    .SUBDIRS: page1 page2 page3 page4
          IMAGES = $(glob *.jpg)
          index.html: $(IMAGES)
              genhtml $+ > $@
>>


File: omake-doc, Node: Subsection 3-6-2,	Next: Subsection 3-6-3,	Prev: Subsection 3-6-1,	Up: Section 3-6


3.6.2  Simplified sub-configurations
====================================

  Another option is to add a configuration file in each of the
subdirectories that defines directory-specific information. For this
example, we might define a file BuildInfo.om in each of the
subdirectories that defines a list of images in that directory. The
.SUBDIRS line is similar, but we include the BuildInfo file.
<<    .SUBDIRS: page1 page2 page3 page4
          include BuildInfo   # Defines the IMAGES variable

          index.html: $(IMAGES)
              genhtml $+ > $@
>>

  Where we might have the following configurations.
<<   page1/BuildInfo.om:
         IMAGES[] = image.jpg
     page2/BuildInfo.om:
         IMAGES[] = ../common/header.jpg winlogo.jpg
     page3/BuildInfo.om:
         IMAGES[] = ../common/header.jpg unixlogo.jpg daemon.jpg
     page4/BuildInfo.om:
         IMAGES[] = fee.jpg fi.jpg foo.jpg fum.jpg
>>


File: omake-doc, Node: Subsection 3-6-3,	Next: Subsection 3-6-4,	Prev: Subsection 3-6-2,	Up: Section 3-6


3.6.3  Computing the subdirectory list
======================================

  The other hardcoded specification is the list of subdirectories page1,
..., page4. Rather than editing the project OMakefile each time a
directory is added, we could compute it (again with glob).
<<    .SUBDIRS: $(glob page*)
          index.html: $(glob *.jpg)
              genhtml $+ > $@
>>

  Alternately, the directory structure may be hierarchical. Instead of
using glob, we could use the subdirs function, returns each of the
directories in a hierarchy. For example, this is the result of
evaluating the subdirs function in the omake project root. The P option,
passed as the first argument, specifies that the listing is "proper," it
should not include the omake directory itself.
<<    osh> subdirs(P, .)
      - : <array
              /home/jyh/.../omake/mk : Dir
              /home/jyh/.../omake/RPM : Dir
              ...
              /home/jyh/.../omake/osx_resources : Dir>
>>

  Using subdirs, our example is now as follows.
<<    .SUBDIRS: $(subdirs P, .)
          index.html: $(glob *.jpg)
              genhtml $+ > $@
>>

  In this case, every subdirectory will be included in the project.
  If we are using the BuildInfo.om option. Instead of including every
subdirectory, we could include only those that contain a BuildInfo.om
file. For this purpose, we can use the find function, which traverses
the directory hierarchy looking for files that match a test expression.
In our case, we want to search for files with the name BuildInfo.om.
Here is an example call.
<<    osh> FILES = $(find . -name BuildInfo.om)
      - : <array
              /home/jyh/.../omake/doc/html/BuildInfo.om : File
              /home/jyh/.../omake/src/BuildInfo.om : File
              /home/jyh/.../omake/tests/simple/BuildInfo.om : File>
      osh> DIRS = $(dirof $(FILES))
      - : <array
              /home/jyh/.../omake/doc/html : Dir
              /home/jyh/.../omake/src : Dir
              /home/jyh/.../omake/tests/simple : Dir>
>>

  In this example, there are three BuildInfo.om files, in the doc/html,
src, and tests/simple directories. The dirof function returns the
directories for each of the files.
  Returning to our original example, we modify it as follows.
<<    .SUBDIRS: $(dirof $(find . -name BuildInfo.om))
          include BuildInfo   # Defines the IMAGES variable

          index.html: $(IMAGES)
              genhtml $+ > $@
>>


File: omake-doc, Node: Subsection 3-6-4,	Prev: Subsection 3-6-3,	Up: Section 3-6


3.6.4  Temporary directories
============================

  Sometimes, your project may include temporary directories--directories
where you place intermediate results. these directories are deleted
whenever the project is cleanup up. This means, in particular, that you
can't place an OMakefile in a temporary directory, because it will be
removed when the directory is removed.
  Instead, if you need to define a configuration for any of these
directories, you will need to define it using a .SUBDIRS body.
<<    section
          CREATE_SUBDIRS = true

          .SUBDIRS: tmp
              # Compute an MD5 digest
              %.digest: %.comments
                 echo $(digest $<) > $@

              # Extract comments from the source files
              %.comments: ../src/%.src
                 grep '^#' $< > $@

              .DEFAULT: foo.digest

      .PHONY: clean

      clean:
          rm -rf tmp        
>>

  In this example, we define the CREATE_SUBDIRS variable as true, so
that the tmp directory will be created if it does not exist. The
.SUBDIRS body in this example is a bit contrived, but it illustrates the
kind of specification you might expect. The clean phony-target indicates
that the tmp directory should be removed when the project is cleaned up.


File: omake-doc, Node: Chapter 4,	Next: Chapter 5,	Prev: Chapter 3,	Up: Top


Chapter 4   OMake concepts and syntax
*************************************
    
  Projects are specified to omake with OMakefiles. The OMakefile has a
format similar to a Makefile. An OMakefile has three main kinds of
syntactic objects: variable definitions, function definitions, and rule
definitions.
* Menu:

* Section 4-1::	Variables
* Section 4-2::	Adding to a variable definition
* Section 4-3::	Arrays
* Section 4-4::	Special characters and quoting
* Section 4-5::	Function definitions
* Section 4-6::	Curried functions
* Section 4-7::	Comments
* Section 4-8::	File inclusion
* Section 4-9::	Scoping, sections
* Section 4-10::	Conditionals
* Section 4-11::	Matching
* Section 4-12::	Objects
* Section 4-13::	Classes
* Section 4-14::	Inheritance
* Section 4-15::	static.
* Section 4-16::	Constants


File: omake-doc, Node: Section 4-1,	Next: Section 4-2,	Up: Chapter 4


4.1  Variables
**************

   
  Variables are defined with the following syntax. The name is any
sequence of alphanumeric characters, underscore _, and hyphen -.
<<   <name> = <value>
>>

  Values are defined as a sequence of literal characters and variable
expansions. A variable expansion has the form $(<name>), which
represents the value of the <name> variable in the current environment.
Some examples are shown below.
<<   CC = gcc
     CFLAGS = -Wall -g
     COMMAND = $(CC) $(CFLAGS) -O2
>>

  In this example, the value of the COMMAND variable is the string gcc
-Wall -g -O2.
  Unlike make(1), variable expansion is eager and pure (see also the
section on Scoping). That is, variable values are expanded immediately
and new variable definitions do not affect old ones. For example,
suppose we extend the previous example with following variable
definitions.
<<   X = $(COMMAND)
     COMMAND = $(COMMAND) -O3
     Y = $(COMMAND)
>>

  In this example, the value of the X variable is the string gcc -Wall
-g -O2 as before, and the value of the Y variable is gcc -Wall -g -O2
-O3.

File: omake-doc, Node: Section 4-2,	Next: Section 4-3,	Prev: Section 4-1,	Up: Chapter 4


4.2  Adding to a variable definition
************************************


  Variables definitions may also use the += operator, which adds the new
text to an existing definition. The following two definitions are
equivalent.
<<   # Add options to the CFLAGS variable
     CFLAGS = $(CFLAGS) -Wall -g

     # The following definition is equivalent
     CFLAGS += -Wall -g
>>


File: omake-doc, Node: Section 4-3,	Next: Section 4-4,	Prev: Section 4-2,	Up: Chapter 4


4.3  Arrays
***********

   
  Arrays can be defined by appending the [] sequence to the variable
name and defining initial values for the elements as separate lines.
Whitespace on each line is taken literally. The following code sequence
prints c d e.
<<    X[] =
          a b
          c d e
          f

      println($(nth 1, $(X)))
>>


File: omake-doc, Node: Section 4-4,	Next: Section 4-5,	Prev: Section 4-3,	Up: Chapter 4


4.4  Special characters and quoting
***********************************

   
  The following characters are special to omake: $():,=#\. To treat any
of these characters as normal text, they should be escaped with the
backslash character \.
<<    DOLLAR = \$
>>

  Newlines may also be escaped with a backslash to concatenate several
lines.
<<    FILES = a.c\
              b.c\
              c.c
>>

  Note that the backslash is not an escape for any other character, so
the following works as expected (that is, it preserves the backslashes
in the string).
<<    DOSTARGET = C:\WINDOWS\control.ini
>>

  An alternative mechanism for quoting special text is the use $"..."
escapes. The number of double-quotations is arbitrary. The outermost
quotations are not included in the text.
<<    A = $""String containing "quoted text" ""
      B = $"""Multi-line
          text.
          The # character is not special"""
>>

  Note that it is not possible to denote the empty string with this
notation. As a workaround, call the string function without parameters,
as in
<<    EMPTY = $(string)
>>


File: omake-doc, Node: Section 4-5,	Next: Section 4-6,	Prev: Section 4-4,	Up: Chapter 4


4.5  Function definitions
*************************

    
  Functions are defined using the following syntax.
<<   <name>(<params>) =
        <indented-body>
>>

  The parameters are a comma-separated list of identifiers, and the body
must be placed on a separate set of lines that are indented from the
function definition itself. For example, the following text defines a
function that concatenates its arguments, separating them with a colon.
<<    ColonFun(a, b) =
          return($(a):$(b))
>>

The return expression can be used to return a
value from the function. A return statement is not required; if it is
omitted, the returned value is the value of the last expression in the
body to be evaluated. NOTE: as of version 0.9.6, return is a control
operation, causing the function to immediately return. In the following
example, when the argument a is true, the function f immediately returns
the value 1 without evaluating the print statement.
<<    f(a) =
         if $(a)
            return 1
         println(The argument is false)
         return 0
>>

In many cases, you may wish to return a value
from a section or code block without returning from the function. In
this case, you would use the value operator. In fact, the value operator
is not limited to functions, it can be used any place where a value is
required. In the following definition, the variable X is defined as 1 or
2, depending on the value of a, then result is printed, and returned
from the function.
<<    f_value(a) =
         X =
            if $(a)
               value 1
            else
               value 2
         println(The value of X is $(X))
         value $(X)
>>

  Functions are called using the GNU-make syntax, $(<name> <args)),
where <args> is a comma-separated list of values. For example, in the
following program, the variable X contains the value foo:bar.
<<   X = $(ColonFun foo, bar)
>>

  If the value of a function is not needed, the function may also be
called using standard function call notation. For example, the following
program prints the string "She says: Hello world".
<<    Printer(name) =
          println($(name) says: Hello world)

      Printer(She)
>>

* Menu:

* Subsection 4-5-1::	Passing parameterized bodies
* Subsection 4-5-2::	Keyword arguments


File: omake-doc, Node: Subsection 4-5-1,	Next: Subsection 4-5-2,	Up: Section 4-5


4.5.1  Passing parameterized bodies
===================================
   
  It is sometimes useful to pass an argument that can be evaluated. For
example, the built-in function foreach takes an array of values, and
runs some code for every array element:
<<    a[] =
          p
          q
      foreach(x => ..., $(a))
          println($"Next element: $(x)")
>>

  Note that you really have to write three dots - this is not an
omission. The three dots reference the indented subsection immediately
following.
  This feature is very similar to passing anonymous functions. However,
there are subtle differences, in particular with respect to scoping. The
parameterized body behaves much like section, and exports of private
(statically-scoped) variables to the enclosing scope are possible.

File: omake-doc, Node: Subsection 4-5-2,	Prev: Subsection 4-5-1,	Up: Section 4-5


4.5.2  Keyword arguments
========================
    
  This feature was introduced in version 0.9.8.6.
  Functions can also have keyword parameters and arguments. The syntax
of a keyword parameter/argument is [~|?]<id> [= <expression>], where the
keyword name <id> is preceeded by the character ~ (for required
arguments), or ? (for optional arguments). If a default value =
<expression> is provided, the argument is always optional.
  Keyword arguments and normal anonymous arguments are completely
separate. Also, it is an error to pass a keyword argument to a function
that does not define it as a keyword parameter.
<<    osh>f(x, ?y = 1, z) =
             add($(mul $x, 100), $(mul $y, 10), $z)
      - : <fun 0>
      osh>f(1, ~y = 2, 3)
      - : 123 : Int
      osh>f(1, 3, ~y = 2)
      - : 123 : Int
      osh>f(1, 3)
      - : 113 : Int
      osh>f(1, 2, 3)
      *** omake error:
         File -: line 11, characters 0-10
         arity mismatch: expected 2 args, got 3
      osh>f(~z = 7)
      *** omake error:
         File -: line 12, characters 0-8
         no such keyword: z
>>

  An optional keyword argument defaults to the empty value.
<<    osh> g(?x) =
               println($">>>$x<<<")
      - : <fun 0>
      osh> g()
      >>><<<
      osh> g(~x = xxx)
      >>>xxx<<<
>>

  It is an error to omit a required keyword argument.
<<    osh> h(~x, ~y) =
               println(x = $x; y = $y)
      - : <fun 0>
      osh> h(~y = 2, ~x = 1)
      x = 1; y = 2
      osh> h(~y = 2)
      *** omake error:
         File -: line 11, characters 0-9
         keyword argument is required: x
>>


File: omake-doc, Node: Section 4-6,	Next: Section 4-7,	Prev: Section 4-5,	Up: Chapter 4


4.6  Curried functions
**********************


  This feature was introduced in version 0.9.8.6.
  Functions that are marked with the classifier curry can be called with
"too many" arguments. It is expected that a curried function returns a
function that consumes the remaining arguments. All arguments must be
specified.
<<    osh>curry.f(x, y) =
              println($"Got two arguments: x = $x, y = $y")
              g(z) =
                 add($x, $y, $z)
      osh> f(1, 2, 3)
      Got two arguments: x = 1, y = 2
      - : 6 : Int
      osh> f(1, 2)
      Got two arguments: x = 1, y = 2
      *** omake error:
         File -: line 62, characters 0-7
         arity mismatch: expected 1 args, got 0
>>

  The function apply can be used to compute partial applications,
whether or not the function is labeled as a curried function.
<<    osh> f1(a, ~b = 2, ~c = 3, d) =
              println($"a = $a, b = $b, c = $c, d = $d")
      - : <fun 0>
      osh> f2 = $(apply $(f1), ~c = 13, 11)
      - : <curry 0>
      osh> f2(14, ~b = 12)
      a = 11, b = 12, c = 13, d = 14
      osh> f2(24)
      a = 11, b = 2, c = 13, d = 24
>>


File: omake-doc, Node: Section 4-7,	Next: Section 4-8,	Prev: Section 4-6,	Up: Chapter 4


4.7  Comments
*************


  Comments begin with the # character and continue to the end of the
line.

File: omake-doc, Node: Section 4-8,	Next: Section 4-9,	Prev: Section 4-7,	Up: Chapter 4


4.8  File inclusion
*******************

   

  Files may be included with the include or open form. The included file
must use the same syntax as an OMakefile.
<<    include $(Config_file)
>>

  The open operation is similar to an include, but the file is included
at most once. 
<<    open Config

      # Repeated opens are ignored, so this
      # line has no effect.
      open Config
>>

  If the file specified is not an absolute filenmame, both include and
open operations search for the file based on the 'OMAKEPATH' variable.
In case of the open directive, the search is performed at parse time,
and the argument to open may not contain any expressions.

File: omake-doc, Node: Section 4-9,	Next: Section 4-10,	Prev: Section 4-8,	Up: Chapter 4


4.9  Scoping, sections
**********************

    
  Scopes in omake are defined by indentation level. When indentation is
increased, such as in the body of a function, a new scope is introduced.
  The section form can also be used to define a new scope. For example,
the following code prints the line X = 2, followed by the line X = 1.
<<    X = 1
      section
          X = 2
          println(X = $(X))

      println(X = $(X))
>>

  This result may seem surprising--the variable definition within the
section is not visible outside the scope of the section.
  The export form, which will be described in detail in
Section 6.3*Note Section 6-3::, can be used to circumvent this
restriction by exporting variable values from an inner scope. For
example, if we modify the previous example by adding an export
expression, the new value for the X variable is retained, and the code
prints the line X = 2 twice.
<<    X = 1
      section
          X = 2
          println(X = $(X))
          export

      println(X = $(X))
>>

  There are also cases where separate scoping is quite important. For
example, each OMakefile is evaluated in its own scope. Since each part
of a project may have its own configuration, it is important that
variable definitions in one OMakefile do not affect the definitions in
another.
  To give another example, in some cases it is convenient to specify a
separate set of variables for different build targets. A frequent idiom
in this case is to use the section command to define a separate scope.
<<   section
        CFLAGS += -g
        %.c: %.y
            $(YACC) $<
        .SUBDIRS: foo

     .SUBDIRS: bar baz
>>

  In this example, the -g option is added to the CFLAGS variable by the
foo subdirectory, but not by the bar and baz directories. The implicit
rules are scoped as well and in this example, the newly added yacc rule
will be inherited by the foo subdirectory, but not by the bar and baz
ones; furthermore this implicit rule will not be in scope in the current
directory.

File: omake-doc, Node: Section 4-10,	Next: Section 4-11,	Prev: Section 4-9,	Up: Chapter 4


4.10  Conditionals
******************

    

  Top level conditionals have the following form.
<<    if <test>
         <true-clause>
      elseif <test2>
         <elseif-clause>
      else
         <else-clause>
>>

  The <test> expression is evaluated, and if it evaluates to a true
value (see Section 9.2*Note Section 9-2:: for more information on
logical values, and Boolean functions), the code for the <true-clause>
is evaluated; otherwise the remaining clauses are evaluated. There may
be multiple elseif clauses; both the elseif and else clauses are
optional. Note that the clauses are indented, so they introduce new
scopes.
  When viewed as a predicate, a value corresponds to the Boolean false,
if its string representation is the empty string, or one of the strings
false, no, nil, undefined, or 0. All other values are true.
  The following example illustrates a typical use of a conditional. The
OSTYPE variable is the current machine architecture.
<<    # Common suffixes for files
      if $(equal $(OSTYPE), Win32)
         EXT_LIB = .lib
         EXT_OBJ = .obj
         EXT_ASM = .asm
         EXE = .exe
         export
      elseif $(mem $(OSTYPE), Unix Cygwin)
         EXT_LIB = .a
         EXT_OBJ = .o
         EXT_ASM = .s
         EXE =
         export
      else
         # Abort on other architectures
         eprintln(OS type $(OSTYPE) is not recognized)
         exit(1)
>>


File: omake-doc, Node: Section 4-11,	Next: Section 4-12,	Prev: Section 4-10,	Up: Chapter 4


4.11  Matching
**************

    

  Pattern matching is performed with the switch and match forms.
<<    switch <string>
      case <pattern1>
          <clause1>
      case <pattern2>
          <clause2>
      ...
      default
         <default-clause>
>>

  The number of cases is arbitrary. The default clause is optional;
however, if it is used it should be the last clause in the pattern
match.
  For switch, the string is compared with the patterns literally.
<<    switch $(HOST)
      case mymachine
          println(Building on mymachine)
      default
          println(Building on some other machine)
>>

  Patterns need not be constant strings. The following function tests
for a literal match against pattern1, and a match against pattern2 with
## delimiters.
<<   Switch2(s, pattern1, pattern2) =
        switch $(s)
        case $(pattern1)
            println(Pattern1)
        case $"##$(pattern2)##"
            println(Pattern2)
        default
            println(Neither pattern matched)
>>

  For match the patterns are egrep(1)-style regular expressions. The
numeric variables $1, $2, ... can be used to retrieve values that are
matched by \(...\) expressions.
<<    match $(NODENAME)@$(SYSNAME)@$(RELEASE)
      case $"mymachine.*@\(.*\)@\(.*\)"
          println(Compiling on mymachine; sysname $1 and release $2 are
ignored)

      case $".*@Linux@.*2\.4\.\(.*\)"
          println(Compiling on a Linux 2.4 system; subrelease is $1)

      default
          eprintln(Machine configuration not implemented)
          exit(1)
>>


File: omake-doc, Node: Section 4-12,	Next: Section 4-13,	Prev: Section 4-11,	Up: Chapter 4


4.12  Objects
*************

    
  OMake is an object-oriented language. Generally speaking, an object is
a value that contains fields and methods. An object is defined with a .
suffix for a variable. For example, the following object might be used
to specify a point (1, 5) on the two-dimensional plane.
<<    Coord. =
          x = 1
          y = 5
          print(message) =
             println($"$(message): the point is ($(x), $(y)")

      # Define X to be 5
      X = $(Coord.x)

      # This prints the string, "Hi: the point is (1, 5)"
      Coord.print(Hi)
>>

  The fields x and y represent the coordinates of the point. The method
print prints out the position of the point.

File: omake-doc, Node: Section 4-13,	Next: Section 4-14,	Prev: Section 4-12,	Up: Chapter 4


4.13  Classes
*************

   
  We can also define classes. For example, suppose we wish to define a
generic Point class with some methods to create, move, and print a
point. A class is really just an object with a name, defined with the
class directive.
<<    Point. =
          class Point

          # Default values for the fields
          x = 0
          y = 0

          # Create a new point from the coordinates
          new(x, y) =
             this.x = $(x)
             this.y = $(y)
             return $(this)

          # Move the point to the right
          move-right() =
             x = $(add $(x), 1)
             return $(this)

          # Print the point
          print() =
             println($"The point is ($(x), $(y)")

      p1 = $(Point.new 1, 5)
      p2 = $(p1.move-right)

      # Prints "The point is (1, 5)"
      p1.print()

      # Prints "The point is (2, 5)"
      p2.print()
>>

  Note that the variable $(this) is used to refer to the current object.
Also, classes and objects are functional---the new and move-right
methods return new objects. In this example, the object p2 is a
different object from p1, which retains the original (1, 5) coordinates.

File: omake-doc, Node: Section 4-14,	Next: Section 4-15,	Prev: Section 4-13,	Up: Chapter 4


4.14  Inheritance
*****************

   
  Classes and objects support inheritance (including multiple
inheritance) with the extends directive. The following definition of
Point3D defines a point with x, y, and z fields. The new object inherits
all of the methods and fields of the parent classes/objects.
<<    Z. =
         z = 0

      Point3D. =
         extends $(Point)
         extends $(Z)
         class Point3D

         print() =
            println($"The 3D point is ($(x), $(y), $(z))")

      # The "new" method was not redefined, so this
      # defines a new point (1, 5, 0).
      p = $(Point3D.new 1, 5)
>>


File: omake-doc, Node: Section 4-15,	Next: Section 4-16,	Prev: Section 4-14,	Up: Chapter 4


4.15  static.
*************

    
  The static. object is used to specify values that are persistent
across runs of OMake. They are frequently used for configuring a
project. Configuring a project can be expensive, so the static. object
ensure that the configuration is performed just once. In the following
(somewhat trivial) example, a static section is used to determine if the
LaTeX command is available. The $(where latex) function returns the full
pathname for latex, or false if the command is not found.
<<   static. =
        LATEX_ENABLED = false
        print(--- Determining if LaTeX is installed )
        if $(where latex)
            LATEX_ENABLED = true
            export

        if $(LATEX_ENABLED)
           println($'(enabled)')
        else
           println($'(disabled)')
>>

  The OMake standard library provides a number of useful functions for
programming the static. tests, as described in
Chapter 14*Note Chapter 14::. Using the standard library, the
above can be rewritten as
<<   open configure/Configure
     static. =
        LATEX_ENABLED = $(CheckProg latex)
>>

  As a matter of style, a static. section that is used for configuration
should print what it is doing using the 'ConfMsgChecking' and
'ConfMsgResult' functions (of course, most of helper functions in the
standard library would do that automatically).
* Menu:

* Subsection 4-15-1::	.STATIC


File: omake-doc, Node: Subsection 4-15-1,	Up: Section 4-15


4.15.1  .STATIC
===============
     
  This feature was introduced in version 0.9.8.5.
  There is also a rule form of static section. The syntax can be any of
the following three forms.
<<    # Export all variables defined by the body
      .STATIC:
          <body>

      # Specify file-dependencies
      .STATIC: <dependencies>
          <body>

      # Specify which variables to export, as well as file dependencies
      .STATIC: <vars>: <dependencies>
          <body>
>>

  The <vars> are the variable names to be defined, the <dependencies>
are file dependencies---the rule is re-evaluated if one of the
dependencies is changed. The <vars> and <dependencies> can be omitted;
if so, all variables defined in the <body> are exported.
  For example, the final example of the previous section can also be
implemented as follows.
<<    open configure/Configure
      .STATIC:
          LATEX_ENABLED = $(CheckProg latex)
>>
   The effect is much the same as using static. (instead of .STATIC).
However, in most cases .STATIC is preferred, for two reasons.
  First, a .STATIC section is lazy, meaning that it is not evaluated
until one of its variables is resolved. In this example, if
$(LATEX_ENABLED) is never evaluated, the section need never be evaluated
either. This is in contrast to the static. section, which always
evaluates its body at least once.
  A second reason is that a .STATIC section allows for file
dependencies, which are useful when the .STATIC section is used for
memoization. For example, suppose we wish to create a dictionary from a
table that has key-value pairs. By using a .STATIC section, we can
perform this computation only when the input file changes (not on every
fun of omake). In the following example the 'awk' function is used to
parse the file table-file. When a line is encountered with the form key
= value, the key/value pair is added the the TABLE.
<<    .STATIC: table-file
          TABLE = $(Map)
          awk(table-file)
          case $'^\([[:alnum:]]+\) *= *\(.*\)'
              TABLE = $(TABLE.add $1, $2)
              export
>>

  It is appropriate to think of a .STATIC section as a rule that must be
recomputed whenever the dependencies of the rule change. The targets of
the rule are the variables it exports (in this case, the TABLE
variable).


4.15.1.1  .MEMO
---------------
     
  A .MEMO rule is just like a .STATIC rule, except that the results are
not saved between independent runs of omake.


4.15.1.2  :key:
-------------------------------------------------
   
  The .STATIC and .MEMO rules also accept a :key: value, which specifies
a "key" associated with the values being computed. It is useful to think
of a .STATIC rule as a dictionary that associates keys with their
values. When a .STATIC rule is evaluated, the result is saved in the
table with the :key: defined by the rule (if a :key: is not specified, a
default key is used instead). In other words, a rule is like a function.
The :key: specifies the function "argument", and the rule body computes
the result.
  To illustrate, let's use a .MEMO rule to implement a Fibonacci
function.
<<    fib(i) =
          i = $(int $i)
          .MEMO: :key: $i
              println($"Computing fib($i)...")
              result =
                  if $(or $(eq $i, 0), $(eq $i, 1))
                      value $i
                  else
                      add($(fib $(sub $i, 1)), $(fib $(sub $i, 2)))
          value $(result)

      println($"fib(10) = $(fib 10)")
      println($"fib(12) = $(fib 12)")
>>
   When this script is run, it produces the following output.
<<    Computing fib(10)...
      Computing fib(9)...
      Computing fib(8)...
      Computing fib(7)...
      Computing fib(6)...
      Computing fib(5)...
      Computing fib(4)...
      Computing fib(3)...
      Computing fib(2)...
      Computing fib(1)...
      Computing fib(0)...
      fib(10) = 55
      Computing fib(12)...
      Computing fib(11)...
      fib(12) = 144
>>
   Note that the Fibonacci computation is performed just once for each
value of the argument, rather than an exponential number of times. In
other words, the .MEMO rule has performed a memoization, hence the name.
Note that if .STATIC were used instead, the values would be saved across
runs of omake.
  As a general guideline, whenever you use a .STATIC or .MEMO rule
within a function body, you will usually want to use a :key: value to
index the rule by the function argument. However, this is not required.
In the following, the .STATIC rule is used to perform some expensive
computation once.
<<    f(x) =
          .STATIC:
              y = $(expensive-computation)
          add($x, $y)
>>

  Additonal care should be taken for recursive functions, like the
Fibonacci function. If the :key: is omitted, then the rule would be
defined in terms of itself, resulting in a cyclic dependency. Here is
the output of the Fibonacci program with an omitted :key:.
<<    Computing fib(10)...
      Computing fib(8)...
      Computing fib(6)...
      Computing fib(4)...
      Computing fib(2)...
      Computing fib(0)...
      fib(10) = 0
      fib(12) = 0
>>
   The reason for this behavior is that the result value is not saved
until the base case i = 0 || i = 1 is reached, so fib calls itself
recursively until reaching fib(0), whereupon the result value is fixed
at 0.
  In any case, recursive definitions are perfectly acceptable, but you
will usually want a :key: argument so that each recursive call has a
different :key:. In most cases, this means that the :key: should include
all arguments to the function.

File: omake-doc, Node: Section 4-16,	Prev: Section 4-15,	Up: Chapter 4


4.16  Constants
***************

   
  Internally, OMake represents values in several forms, which we list
here.


   - int


      - Constructor: $(int <i>) 9.4.1*Note Subsection 9-4-1::. 
      - Object: Int 12.1.4*Note Subsection 12-1-4::. 
      - An integer is a represented with finite precision using the
      OCaml representation (31 bits on a 32 platform, and 63 bits on a
      64 bit platform). 
      - See also: arithmetic 9.4.3*Note Subsection 9-4-3::. 


   - float


      - Constructor: $(float <x>) 9.4.2*Note Subsection 9-4-2::. 
      - Object: Float 12.1.5*Note Subsection 12-1-5::. 
      - A float is a floating-point value, represented in IEEE 64-bit
      format. 
      - See also: arithmetic 9.4.3*Note Subsection 9-4-3::. 


   - array


      - Constructor: $(array <v1>, ...,
      <vn>) 9.3.1*Note Subsection 9-3-1::. 
      - Object: Array 12.1.7*Note Subsection 12-1-7::. 
      - An array is a finite list of values. Arrays are also defined
      with an array definition 
      <<    X[] =
                <v1>
                ...
                <vn>
      >>

      - See also: nth 9.3.5*Note Subsection 9-3-5::,
      nth-tl 9.3.8*Note Subsection 9-3-8::,
      length 9.3.4*Note Subsection 9-3-4::, ... 


   - string


      - Object: String 12.1.8*Note Subsection 12-1-8::. 
      - By default, all constant character sequences represent strings,
      so the simple way to construct a string is to write it down.
      Internally, the string may be parsed as several pieces. A string
      often represents an array of values separated by whitespace. 
      <<    osh>S = This is a string
            - : <sequence
               "This" : Sequence
               ' ' : White
               "is" : Sequence
               ' ' : White
               "a" : Sequence
               ' ' : White
               "string" : Sequence>
               : Sequence
            osh>length($S)
            - : 4 : Int
      >>


      - A data string is a string where whitespace is taken literally.
      It represents a single value, not an array. The constructors are
      the quotations $"..." and $'...'.
      <<    osh>S = $'''This is a string'''
            - : <data "This is a string"> : String
      >>


      - See also: Quoted strings 7.2*Note Section 7-2::.



   - file


      - Constructor: $(file <names>) 10.1.1*Note Subsection 10-1-1::. 
      - Object: File 12.1.13*Note Subsection 12-1-13::. 
      - A file object represents the abstract name for a file. The file
      object can be viewed as an absolute name; the string
      representation depends on the current directory.
      <<    osh>name = $(file foo)
            - : /Users/jyh/projects/omake/0.9.8.x/foo : File
            osh>echo $(name)
            foo
            osh>cd ..
            - : /Users/jyh/projects/omake : Dir
            osh>echo $(name)
            0.9.8.x/foo
      >>


      - See also: vmount 10.6.1*Note Subsection 10-6-1::. 


   - directory


      - Constructor: $(dir <names>) 10.1.1*Note Subsection 10-1-1::. 
      - Object: Dir 12.1.14*Note Subsection 12-1-14::. 
      - A directory object is like a file object, but it represents a
      directory. 


   - map (dictionary) 

      - Object: Map 12.1.2*Note Subsection 12-1-2::. 
      - A map/dictionary is a table that maps values to values. The Map
      object is the empty map. The data structure is persistent, and all
      operations are pure and functional. The special syntax $|key| can
      be used for keys that are strings.
      <<    osh>table = $(Map)
            osh>table = $(table.add x, int)
            osh>table. +=
                    $|y| = int
            osh>table.find(y)
            - : "int" : Sequence
      >>



   - channel


      - Constructor: $(fopen <filename>,
      <mode>) 10.8.4*Note Subsection 10-8-4::. 
      - Objects: InChannel 12.1.16*Note Subsection 12-1-16::,
      OutChannel 12.1.17*Note Subsection 12-1-17::. 
      - Channels are used for buffered input/output. 


   - function


      - Constructor: $(fun <params> =>
      <body>) 9.5.1*Note Subsection 9-5-1::. 
      - Object: Fun 12.1.9*Note Subsection 12-1-9::. 
      - Functions can be defined in several ways. 

         - As an anonymous function, 
         <<    $(fun i, j => $(add $i, $j))
         >>

         - As a named function, 
         <<    f(i, j) =
                   add($i, $j)
         >>

         - (This feature was introduced in version 0.9.8.6.) As an
         anonymous function argument. 
         <<    osh>foreach(i => $(add $i, 1), 1 2 3)
               - : <array 2 3 4> : Array
         >>




   - lexer


      - Object: Lexer 10.11.9*Note Subsection 10-11-9::. 
      - This object represents a lexer. 


   - parser


      - Object: Parser 10.11.13*Note Subsection 10-11-13::. 
      - This object represents a parser. 




File: omake-doc, Node: Chapter 5,	Next: Chapter 6,	Prev: Chapter 4,	Up: Top


Chapter 5   Variables and Naming
********************************
    
  During evaluation, there are three different kinds of namespaces.
Variables can be private, or they may refer to fields in the current
this object, or they can be part of the global namespace. The namespace
can be specified directly by including an explicit qualifier before the
variable name. The three namespaces are separate; a variable can be
bound in one or more simultaneously.
<<    # private namespace
      private.X = 1
      # current object
      this.X = 2
      # public, globally defined
      global.X = 3
>>

* Menu:

* Section 5-1::	private.
* Section 5-2::	this.
* Section 5-3::	global.
* Section 5-4::	protected.
* Section 5-5::	public.
* Section 5-6::	Qualified blocks
* Section 5-7::	declare


File: omake-doc, Node: Section 5-1,	Next: Section 5-2,	Up: Chapter 5


5.1  private.
*************

   
  The private. qualifier is used to define variables that are private to
the current file/scope. The values are not accessible outside the scope.
Private variables are statically (lexically) scoped.
   Unforunately, private variables have always been incorrectly
implemented in every omake version. Read the section below on the
issues. In version 0.10 the problems still exist, and will probably be
tackled in 0.11. 
<<    Obj. =
         private.X = 1

         print() =
            println(The value of X is: $X)

      # Prints:
      #    The private value of X is: 1
      Obj.print()

      # This is an error--X is private in Obj
      y = $(Obj.X)
>>

  In addition, private definitions do not affect the global value of a
variable.
<<   # The public value of x is 1
     x = 1

     # This object uses a private value of x
     Obj. =
         private.x = 2

         print() =
            x = 3
            println(The private value of x is: $x)
            println(The public value of x is: $(public.x))
            f()

     # Prints:
     #    The private value of x is: 3
     #    The public value of x is: 1
     Obj.print()
>>

  Private variables have two additional properties.


   1. Private variables are local to the file in which they are defined.

   2. Private variables are not exported by the export directive, unless
   they are mentioned explicitly in the export directive.
   <<       private. =
               FLAG = true

            section
               FLAG = false
               export

            # FLAG is still true
            section
               FLAG = false
               export FLAG

            # FLAG is now false
       >>


  As mentioned above, there are issues with private variables. In
particular, when a function closure is built, the current values are
remembered with the closure, and any future updates are not seen. For
example:
<<    private.X = foo
      f() =
          println($"The value of X is $(X)")
      f()
      X = bar
      f()
>>

  This prints foo twice! As this is probably not what you want, the
recommendation is: 


   - Use private variables only within functions, and do not expect that
   updates work across function boundaries. 
   - Do not export private variables at the end of a function. 
   - If you want to pass an anonymous function around, and want to
   export some private variable, consider to use the => notation (see
   Section 4.5.1*Note Subsection 4-5-1::). 

  These issues will likely be fixed soon.

File: omake-doc, Node: Section 5-2,	Next: Section 5-3,	Prev: Section 5-1,	Up: Chapter 5


5.2  this.
**********

   
  The this. qualifier is used to define fields that are local to an
object. Object variables are dynamically scoped.
<<    X = 1
      f() =
         println(The public value of X is: $(X))

      # Prints:
      #    The public value of X is: 2
      section
         X = 2
         f()

      # X is a protected field in the object
      Obj. =
         this.X = 3

         print() =
            println(The value of this.X is: $(X))
            f()

      # Prints:
      #    The value of this.X is: 3
      #    The public value of X is: 1
      Obj.print()

      # This is legal, it defines Y as 3
      Y = $(Obj.X)
>>

  In general, it is a good idea to define object variables as protected.
The resulting code is more modular because variables in your object will
not produce unexpected clashes with variables defined in other parts of
the project.

File: omake-doc, Node: Section 5-3,	Next: Section 5-4,	Prev: Section 5-2,	Up: Chapter 5


5.3  global.
************

   
  The global. qualifier is used to specify global dynamically-scoped
variables. In the following example, the global. definition specifies
that the binding X = 4 is to be dynamically scoped. Global variables are
not defined as fields of an object.
<<    X = 1
      f() =
         println(The global value of X is: $(X))

      # Prints:
      #    The global value of X is: 2
      section
         X = 2
         f()

      Obj. =
         this.X = 3

         print() =
            println(The protected value of X is: $(X))
            global.X = 4
            f()

      # Prints:
      #    The protected value of X is: 3
      #    The global value of X is: 4
      Obj.print()
>>


File: omake-doc, Node: Section 5-4,	Next: Section 5-5,	Prev: Section 5-3,	Up: Chapter 5


5.4  protected.
***************

   
  In OMake 0.9.8, protected is a synonym for this.
<<    osh>protected.x = 1
      - : "1" : Sequence
      osh>value $(this.x)
      - : "1" : Sequence
>>
   In 0.9.9, this will change, so that the qualifier protected means (in
0.9.9) that a variable is local to the current object or file, and may
not be accessed outside it.

File: omake-doc, Node: Section 5-5,	Next: Section 5-6,	Prev: Section 5-4,	Up: Chapter 5


5.5  public.
************

   
  In OMake 0.9.8, public is a synonym for global.
<<    osh>public.x = 1
      - : "1" : Sequence
      osh>value $(global.x)
      - : "1" : Sequence
>>
   In 0.9.9, this will change, so that the qualifier public means (in
0.9.9) that a variable is to be accessible from outside the current file
or object.

File: omake-doc, Node: Section 5-6,	Next: Section 5-7,	Prev: Section 5-5,	Up: Chapter 5


5.6  Qualified blocks
*********************


  If several qualified variables are defined simultaneously, a block
form of qualifier can be defined. The syntax is similar to an object
definition, where the name of the object is the qualifier itself. For
example, the following program defines two private variables X and Y.
<<    private. =
          X = 1
          Y = 2
>>
   The qualifier specifies a default namespace for new definitions in
the block. The contents of the block is otherwise general.
<<    private. =
          X = 1
          Y = 2
          public.Z = $(add $X, $Y)
          # Prints "The value of Z is 3"
          echo The value of Z is $Z
>>
   Stylistically, it is usually better to avoid large qualified blocks
because the qualifier status can be easy to forget. For example,
consider the following fragment.
<<    private. =
          # Large code sequence
          ...
          # build foo.o with -g option (ERROR)
          CFLAGS = -g
          foo.o:
>>
   In this case, the programmer probably forgot that the definition of
the variable CFLAGS is in the private block, so a fresh variable
private.CFLAGS is being defined, not the global one. The target foo.o
does not use this definition of CFLAGS.

File: omake-doc, Node: Section 5-7,	Prev: Section 5-6,	Up: Chapter 5


5.7  declare
************

   
  When a variable name is unqualified, its namespace is determined by
the most recent definition or declaration that is in scope for that
variable. We have already seen this in the examples, where a variable
definition is qualified, but the subsequent uses are not qualified
explicitly. In the following example, the first occurrence of $X refers
to the private definition, because that is the most recent. The public
definition of X is still 0, but the variable must be qualified
explicitly in order to access the public value.
<<    public.X = 0
      private.X = 1

      public.print() =
          println(The value of private.X is: $X)
          println(The value of public.X is: $(public.X))
>>
   Sometimes it can be useful to declare a variable without defining it.
For example, we might have a function that uses a variable X that is to
be defined later in the program. The declare directive can be used for
this.
<<    declare public.X

      public.print() =
          println(The value of X is $X)

      # Prints "The value of X is 2"
      X = 2
      print()
>>

  Finally, what about variables that are used but not explicitly
qualified? In this case, the following rules are used.


   - If the variable is a function parameter, it is private. 
   - If the variable is defined in an object, it is qualified with
   this.. 
   - Otherwise, the variable is public. 



File: omake-doc, Node: Chapter 6,	Next: Chapter 7,	Prev: Chapter 5,	Up: Top


Chapter 6   Expressions and values
**********************************
    
  omake provides a full programming-language including many system and
IO functions. The language is object-oriented -- everything is an
object, including the base values like numbers and strings. The omake
language can be characterized as follows:


   - Scoping is by default dynamic. 
   - The language is mostly functional, and side effects on variables
   are normally passed on from scope to scope via an explicit export
   directive, instead of directly mutating variables 
   - Evaluation is normally eager -- that is, expressions are evaluated
   as soon as they are encountered. 

  To illustrate these features, we will use the osh(1) omake program
shell. The osh(1) program provides a toploop, where expressions can be
entered and the result printed. osh(1) normally interprets input as
command text to be executed by the shell, so in many cases we will use
the value form to evaluate an expression directly.
<<    osh> 1
      *** omake error: File -: line 1, characters 0-1 command not found:
1
      osh> value 1
      - : "1" : Sequence
      osh> ls -l omake
      -rwxrwxr-x  1 jyh jyh 1662189 Aug 25 10:24 omake*
>>

* Menu:

* Section 6-1::	Dynamic scoping
* Section 6-2::	Functional evaluation
* Section 6-3::	Exporting the environment
* Section 6-4::	Objects
* Section 6-5::	Field and method calls
* Section 6-6::	Method override
* Section 6-7::	Super calls

