Expressions

MAXScript is an expression-based language. Every construct in the language is an expression and yields a result; this includes constructs that other languages consider statements. The simplified syntax of the language allows you to build very expressive code. Anywhere you can write an <expr> expression, you can write any construct in MAXScript.

A good example of this is the if construct. In statement-based languages, there is usually one syntax for if statements and another for conditional expressions. In MAXScript, a single syntax is used for both cases.

For example,

the following two lines of code are both valid, and their meaning should be obvious:

if a > b then print c else print d

x = if a > b then c else d

You can also write the following line, containing a nested if expression and a nested assignment, which itself is an expression:

x = if (if a > b then c else d) < e then f else (g = 23)

Another example is the block-expression, denoted <block_expr>. It contains a series of <expr> expressions enclosed in parentheses,

For example:

(

print a

print b

if a > b then print "the big a"

)

Each expression in the block is separated by a line break. You can also write several expressions on one line using a ";" (semicolon) to separate them:

(print a; print b; if a > b then print "the big a")

Block-expressions are themselves <expr> expressions. They evaluate their component expressions in sequence and yield as their value the value of the last expression in the block.

To create classic block-structured statements,

you might write:

if a > b then

(

print c

x = sqrt (c)

)

else

(

print d

x = sin (e)

)

or, use a nested block-expression to compute a comparison operand,

for example

if a > (y = sin b; sqrt(y * z)) then print c

At its simplest, a MAXScript program is made up of <expr> expressions. An <expr> is defined as any of the following:

<simple_expr>

<variable_decls>

<assignment>

<context_expr>

<if_expr>

<while_loop>

<do_loop>

<for_loop>

<loop_exit>

<case_expr>

<try_expr>

<function_def>

<function_return>

<struct_def>

<max_command>

<utility_def>

<rollout_def>

<tool_def>

<rcmenu_def>

<plugin_def>

This list of expressions constitute the main constructs in MAXScript.

See also

Simple Expressions

Context Expressions

Controlling Program Flow

Creating Functions

Structure Definition

Literal Constants

Variables - Assignment and Scope

3ds Max Commands

Scripted Utilities

Utility Clauses

Scripted Mouse Tools

Scripted Right-Click Menus

Scripted Plug-ins