What is a macro Scheme?
A macro is a symbol that has a transformer procedure associated with it. When Scheme encounters a macro-expression — i.e., a form whose head is a macro —, it applies the macro’s transformer to the subforms in the macro-expression, and evaluates the result of the transformation.
How are macros implemented?
The trick to implementation a macro system is to tell your compiler to be lazy. Put in another way, when the compiler encounters a function, it first evaluates its formal parameter list, yields the results and passes them to the function.
What is begin in scheme?
Scheme begin expressions aren’t just code blocks, though, because they are expressions that return a value. A begin returns the value of the last expression in the sequence. For example, the begin expression above returns the value returned by the call to bar . The bodies of procedures work like begin s as well.
What is macro example?
Macro is defined as something that covers a large amount, or is large in size. An example of macro is the study of the key driving aspects of an economy; macro economics. An example of macro is a very close up photograph of an ant; a macro photograph.
What are macros used for?
Macros are a set of stored functions that can be used to automate processes that are repeated often. They are tools which can be used to perform most of the redundant tasks with relative ease.
What is begin in racket?
Sequencing in The Racket Guide introduces begin and begin0. syntax. (begin form …) (begin expr …+) The first form applies when begin appears at the top level, at module level, or in an internal-definition position (before any expression in the internal-definition sequence).
Why do we use macro?
Answer: A macro is used to automate a task that you perform repeatedly or on a regular basis. You can record or build a macro and then run it to automatically repeat that series of steps or actions. Tasks performed by macros are typically repetitive in nature and can provide significant time savings.
What is macro and its advantage?
A macro is a name given to a block of C statements as a pre-processor directive. Being a pre-processor, the block of code is communicated to the compiler before entering into the actual coding (main () function). The advantage of using macro is the execution speed of the program fragment.