# Lesson files

If you want to write lesson files, my advise is to look at some of the files in `lesson-files/` and use this document and the music format spec for reference. To use the lesson files, you have to save them in `$HOME/lessonfiles/`.

## File encoding

New in version 2.0 is that Solfege by default expect the content of lesson files to be in UTF-8 encoding. gedit is a nice little editor that let you edit unicode files.

If you don't like unicode, you can tell Solfege that the file has another encoding by inserting a special comment line as the first line of the file. The following example set the charset to ISO 8859-1, a charset commonly used in many west-european language:

    # -*- coding: iso-8859-1 -*-

Russians might wan't to use koi8-r:

    # -*- coding: koi8-r -*-

The program use the python libs to convert to unicode, so it should understand almost any encoding you can think of. If you see some characters are missing, for example when the name of questions are displayed on buttons, then most likely you have done somethings from with the encoding.

## Lesson file contents

A lesson file contains of a header block and one or more question blocks:

    header {
      ASSIGNMENT
      ASSIGNMENT
      ...
    }
    question {
      ASSIGNMENT
      ...
    }

## Header block

The header block can be placed anywhere in the file, but by convention it should be the first block in the file. If more that one header block is found, for example when using the `include` function, only the first header block is used, the rest are ignored.

Definitions to put in the header block:

`version = STRING`

  Tell the oldest version of solfege the lessonfile is known to work with. For example `version = "1.1.1"` This variable is not required, but it should be used because it can (but don't guarantee to) help avoid trouble if the lesson file format changes in the future.

`title = STRING`

  Short oneline description.

`description = STRING`

  Long description that can contain html tags.

`content = LIST`

  Possible values: `chord`, `dictation`, `id-by-name`, `harmony` and `sing-chord`

  Some lessonfiles can be useful for more than one exercise. For example, a file with chords can also be used by the id-by-name exercise, and should have: `content = chord, id-by-name`

`musicformat = normal | chord | satb`
  `normal`

    The default value.

  `chord`

    Any music "MUSIC CODE" will be interpreted as:

        \staff{ < MUSIC CODE > }

    or:

        \staff\transpose NOTENAME{ < MUSIC CODE > }

    `chord` format is necessary if lesson files written for the chord exercise should be used by for example the id-by-name exercise.

  `satb`

    the music `"c | bes g | e | G C"` will be interpreted as:

        \staff{ \stemUp < c > }
        \addvoice{ \stemDown < bes g > }
        \staff{\clef bass; \stemUp < e > }
        \addvoice{ \stemDown < G C > }

    This is used by the sing-chord exercise.

`random_transpose = [key|semitones|accidentals], INTEGER, INTEGER | no | yes`

  In some exercises the program can transpose the music to create variation. The variable is ignored in exercises that does not support transposing.

  `random_transpose = no`

    This is the default value. No transposition will be done.

  `random_transpose = yes`

    The exercise will do random transposition. What kind of transposition depends on the exercise, but you get a ok result from this.

  `random_transpose = accidentals, INTEGER, INTEGER`

    Transpose the music by random. But make sure the number of flats or sharps are within the range specified by `INTEGER, INTEGER`. To explain how this works, think of flats as negative numbers and sharps as positive numbers. The code

        random_transpose = accidentals, -2, 3

    will give you questions with 1 or 2 flats, 0 accidentals or 1, 2 or 3 sharps. The code

        random_transpose = accidentals, 2, 3

    will create questions with two or three sharps.

    Please notice that the music in the lessonfile has to be in c major or a minor for this to work correctly.

  `random_transpose = key, INTEGER1, INTEGER2`

    Transpose the music `INTEGER1` steps down or `INTEGER2 steps` steps up the circle of fifth. (And by my own definition, up is more sharps and down is more flats ... :-) )

  `random_transpose = semitones, INTEGER1, INTEGER2`

    Transpose the music at most `INTEGER1` steps down or `INTEGER2` steps down. The code

        random_transpose = semitones, -2, 6

    will transpose the questions no more than 2 semitones down and 6 semitones up. This is the same as the old `random_transpose = INTEGER, INTEGER` syntax.
`labelformat = normal | progression`

  (Default: normal)

### For "Id by name" exercise only

`filldir = horiz | vertic`

  Tell the direction the buttons are filled. Default value is `vertic`.

`fillnum = INTEGER`

  Tell how many buttons there are in each row or column.

## Question block

`name = "some short name"`

  Questions written for id-by-name and chord exercise need a name.

`music = "\staff{c'2 g' e4 e c1}"`

  The music in the question. Note that there is a shortcut. Instead of:

      question {
         tempo = 160/4
         name = "Lisa gikk til skolen"
         music = "\staff\relative c'{c d e f g2 g2}"
      }

  you can write:

      question {
         tempo = 160/4
         name = "Lisa gikk til skolen"
         "\staff\relative c'{c d e f g2 g2}"
      }

`tempo = 130/4`

  beats per minute / notelen per beat

### Chord questions only

In lesson files that is written to work with `chord` exercise, two more variables can used:

`inversion`

  0 = root position, 1 = first inversion etc.

`toptone`

  1, 3, 5, 7

### Dictation exercise

By default, the dictation exercise will show the first column of music, and then the user should write the rest. But if the first column is not good enough, if there for example are only rests on the first beat, these two variables can tell the program how much music to display:

`clue_end = nn/dd`

  `clue_end=1/4` will display all music in the first quarter note.

`clue_music = MUSIC`

  Write the exact music you want to display. If for example you want to display the whoe bar in the upper staff, and only one note in the lower staff.

(Use only one if these variables in a question. Using both are undefined.)

### Sing chord exercise

Questions for this exercise need to have the `key` variable set if the key signature is anything else than c major (or a minor). Example:

    question { "c''|e'|g|c" }
    question { "a'|e'|c'|a" }
    question { key="d \major" "a'|fis'|d'|d"}
    question { key="f \minor" "as'|f'|c'|f"}

## Global variables

Global variables can save you a few key strokes.

    s = "\score\relative c'{ %s }

    question {
      # instead of music = "\score\relative c'{ c d e f g2 g2 } :
      music = s % "c d e f g2 g"
    }

The global variable `tempo` will be the default tempo for the questions following the definition. If not set, the default value is 120 beats per minute. That equals the definition:

    tempo = 60/4

## Comments

Everything after # on a line is ignored

## Grammar

Disclaimer: I don't know any of the standard ways of describing grammar, like BNF. So this is just an attemt to describe the file format to get people started writing lesson files.

Lessonfiles consists of assignment statements and blocks containing assignment statements.

### Functions

`_`

  takes a string as its only argument. Use this if you want Solfege to translate the string for you. Example:

      description = _("This is a short description")

`include`

  includes another file in to this file. Example:

      include(singchord-1)

### Types

`string`

  is quoted using the `"` character, like this: `"this is a string"`. Use tripple quotes for strings that contain line breaks:

      description = """<h1>Long desription<h1>
                     This lessonfile need very much descriptions.
                     bla bla bla"""

  If the string need to contain the `"` character, you have to use tripple quotes:

      description = """Try <a href="solfege:practise/melodic-interval">this
      </a> for a simpler interval exercise."""

  NB: All strings have to be unicode strings. You can change the encoding of a file using the `iconv` program:

          iconv -f YOUR_ENCODING -t utf8 your.file

`integer`

  is an integer is an integer...

`tempotype (in lack of a better name)`

  is entered as `bpm/beatlen`. An example:

      tempo = 120/4

  will set the tempo to 120 beats per minute, each beat being a quarter note.

### Operators

Operators can only be used on strings

`+`

  is used for joining strings

`%`

  is similar to what you find in python, but it is very limited. It only know about `%s`. One example:

      "\staff\relative c'{%s}" % "c d e"

  evaluates to

      "\staff\relative c'{c d e}"

### Reserved words

To be put on the right side of assignments. The current parser does not complain if you redefines the identifiers, so don't do that!

`chord, dictation, id-by-name, sing-chord`

  Possible values for `content`

`horiz, vertic`

  Used for table filling in id-by-name exercise

`normal, progression`

  `labelformat` values.

### Identifiers

Identifiers match the regular expression "[a-zA-Z]+[\w_-]*".

### Block

There are two block types, `header` and `question`.

    blocktype {
      CONTENTS
    }