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The Map command is also useful for conditional editing of parameter values. By using the conditional operators when and unless, the Map command may be used to gather information or edit material only in the event that some condition holds true or false for the currently mapped object. That is, conditional operators cause one or more clauses to be evaluated only if some test evaluates true or false. It is possible to make more than one clause conditional on a single test and to specify mixtures of conditional and independent clauses. Conditional editing is particularly useful for modifying material that has been algorithmically specified but that the composer subsequently wishes to change, or 'clean up'. For example, the composer from the previous paragraph might have decided that the 1000 gongs sound nice, except that in the second half of the material the tones longer than .5 seconds and higher then 880 Hz have too much brightness. How can the appropriate parameter values be modified if the composer does not know exactly which sound events contain the problem?
scale index (interpolate $note 880 .5 2400 .1)
The Map command functions by applying a series of clauses to each object in a specified reference. Clauses may be independent or conditional. A clause generally consists of an operator and one or more expressions to evaluate in the context of the currently mapped element. There are three broad categories of clause operators. Information operators collect information about the objects mapped and return the results in a table. Command operators allow all the editor's data processing commands to be used as mapping clauses. Clause operators connect clauses together. Here is a summary of the various mapping operators and their syntax:
Information operators:
collect expr sum expr count expr minimize expr maximize expr lowest expr highest expr average expr find expr |