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Inter-Office Memorandum To Mesa Users Date May 31, 1978 From Barbara Koalkin Location Palo Alto Subject Mesa 4.0 Debugger Update Organization SDD/SD XEROX Filed on: [IRIS]DOC>DEBUGGER40.BRAVO This release of the Mesa debugger introduces many changes of interest and importance to all Mesa programmers. The purpose of this memo is to make you aware of the changes that have taken place. More complete explanations may be found in the Mesa Debugger Documentation. Interpreter The major addition to the Mesa 4.0 debugger is an interpreter that handles a subset of the Mesa language; it is useful for common operations such as assignments, dereferencing, indexing, field access, addressing, and simple type conversion. It is a powerful extension to the current debugger command language, as it allows you to more closely specify your variables while debugging, thus giving you more complete information with fewer keystrokes. A subset of the Mesa language has been specified as being acceptable to the interpreter (a copy of the grammar is attached to this memo). Statement Syntax Typing space (sp) to the command processor enables interpreting mode. At this point the debugger is ready to interpret any expression that is valid in the (debugger) grammar. Multiple statements are separated by semicolons; the last statement on a line should be followed by a carriage return (CR). If the statement is a simple expression (ie., not an assignment), the result is displayed after evaluation. For example, to perform an assignment and print the result in one command, you would type foo +- expj foo. Loopholes A more concise LOOPHOLE notation has been introduced to make it easy to display arbitrary data in any format. The character "%" is used to denote LOOPHolE[exp, type], with the expression on the left of the %, and the type on the right. For example, the expression foo % short red Foo means LOOPHOLE the type of the variable foo to be a short red Foo and display its value.