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:
(
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:
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