3.3.4 Summary of Common Syntax

This subsection lists the most commonly used Scheme syntactic expressions, simply so that you will recognize common special syntax when you see it. For a full description of each of these syntaxes, follow the appropriate reference.

lambda (see section Lambda: Basic Procedure Creation) is used to construct procedure objects.

define (see section Top Level Variable Definitions) is used to create a new variable and set its initial value.

set! (see section Top Level Variable Definitions) is used to modify an existing variable’s value.

let, let* and letrec (see section Local Variable Bindings) create an inner lexical environment for the evaluation of a sequence of expressions, in which a specified set of local variables is bound to the values of a corresponding set of expressions. For an introduction to environments, see See section The Concept of Closure.

begin (see section Sequencing and Splicing) executes a sequence of expressions in order and returns the value of the last expression. Note that this is not the same as a procedure which returns its last argument, because the evaluation of a procedure invocation expression does not guarantee to evaluate the arguments in order.

if and cond (see section Simple Conditional Evaluation) provide conditional evaluation of argument expressions depending on whether one or more conditions evaluate to “true” or “false”.

case (see section Simple Conditional Evaluation) provides conditional evaluation of argument expressions depending on whether a variable has one of a specified group of values.

and (see section Conditional Evaluation of a Sequence of Expressions) executes a sequence of expressions in order until either there are no expressions left, or one of them evaluates to “false”.

or (see section Conditional Evaluation of a Sequence of Expressions) executes a sequence of expressions in order until either there are no expressions left, or one of them evaluates to “true”.

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