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Advanced Programming Guide

Advanced Programming Guide

Advanced Programming Guide

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Type Specification or TestA.2 Internal Representations of Data Types • 347DCOLON ∧ expr ∧ type − exprMaple syntax: expr :: typeExprLength: 3This structure has three interpretations depending on the context inwhich it is used. When it appears in the header of a procedure definition,it is a typed parameter declaration. When it appears in the local sectionof a procedure or on the left side of an assignment, it is a type assertion.When it appears elsewhere (specifically in a conditional expression), it isa type test.DebugMaple syntax: noneLength: 2 or moreDEBUG ∧ expr ∧ expr . . .This is another internal-only structure. It is used by the kernel whenprinting error traceback information to transmit that information up thecall stack.Equation or Test for EqualityMaple syntax: expr = exprLength: 3EQUATION ∧ expr ∧ exprThis structure has two interpretations depending on the context inwhich it is used. It can be either a test for equality, or a statement ofequality (not to be confused with an assignment).Error StatementERROR∧ exprMaple syntax: error "msg", arg, . . . argLength: 2

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