Manipulating Symbols

 

  This section describes a group of functions which allow the user to query and modify global variables in the Glish system. These functions give users access to the internals of Glish. symbol_set in particular should be used with caution.

In several of these function, a string is passed as a parameter. This string represents the symbol name which is being manipulated. Record member access etc. is not possible with these functions; only global symbol names can be used.

 
symbol_names()
    returns the names of all of the global variables which have been defined.

symbol_names(f)
  if passed a function, f, which takes a single parameter and returns a boolean, this function will apply f to each of the global variables, and only return the names of those for which f returned T. For example:

    symbol_names( is_function )

would return the names of all of the global functions. As another example,

    symbol_names( func (x) {is_numeric(x) && ! is_const(x)} )

would return all of the numeric global variables which are not const.

symbol_value(name)
    this function takes a string, and returns the value of the symbol called name. If name has more then one element, then symbol_value returns the symbol value of each as a field in a record. The field names of the record correspond to the symbol names. If the string has a single element, the value of that symbol is returned.

 

symbol_set(name,value)
    this function assigns the Glish value value to the symbol with the name specified by the name parameter. name must be a string, and should conform to the restrictions on Glish variable names.

symbol_set(rec)
    if passed a record, this function will explode the record field names into global Glish variables. That is, each field name will get mapped to the global symbol that corresponds to the field name. This global symbol would then be assigned the field's value.

symbol_delete(name)
    this function deletes any symbol named name. Note that this is the only way const symbols can be deleted.

is_defined(name)
    this function returns T if there is a symbol called name, otherwise it returns F. This can be used to prevent multiple inclusion of scripts via include.