GSiril

Expressions

Place notation

The simplest example of an expression is a piece of place notation. The syntax for place notation is fairly flexible: a dot (.) is only required where it is needed to separate two non-cross changes, although it may be used to separate any changes; external places can be left implicit; the cross change may be specified -, x or X; and the symbols for bells above 10 may be specified in upper or lower case.

Place notation comes in two types: symmetrical and asymmetrical blocks. Symmetrical blocks must be prefixed & and asymmetric blocks must be prefixed +. Commas may be used to separate blocks of place notation (or indeed any sort of expression). Some examples are given below.

PB = &-6-6-6, +2;     // A plain lead of Plain Bob Minor
Gr = +3.6-6-6-6-6-6;  // A plain lead of Grandsire Minor

References

Expressions may also reference other symbols by name. For example,

lead = &-6-6-6;
p = lead, +2;
b = lead, +4;

(Note that the of p, above, refers to the lead symbol by name. Therefore, if lead were to be redefined as a lead of Double Oxford, p would then refer to a plain lead of Double Oxford.)

Repetition

Repetition can be handled by prefixing an expression with a number, optionally followed by a *. As names may never begin with a digit, it is safe to omit any whitespace between the number and a symbol to be repeated. For example, the expressions in the following four definitions are identical.

course1 = b, 3*p, b;
course2 = b, 3 p, b; 
course3 = b, 3p, b;
course4 = b, p, p, p, b;

Parentheses can be used to group blocks, for example, when they are to be repeated. For example, the standard 120 of Plain Bob Minor, could be written as follows.

touch = 2(b, 3p, b);

Formatted output

In addition to place notation, expressions may contain strings that are to be printed whilst proving the composition. String literals are put in double quotes, "like this". Several characters, or sequences of characters have special meanings when included in string literals. These are listed below.

@     Prints the current row
$$    Terminate the current proof immediately
$     Prints the number of repeated rows
#     Prints the total number of rows
\n    Prints a new line character
\t    Prints a tab character
\'    Prints a literal " sign [sic]
\x    Prints a literal x character (for any other x).

Ordinarily, string literals will end with an implicit new line character; to suppress this put a backslash immediately before the closing double quote of the string.

A common use of string literals is for outputting information about the touch being proved. For example, these definitions of p and b will print out the lead heads, together with a dash to mark bobbed leads.

p = lead, +2, "  @";
b = lead, +4, "- @";