Operators

MiniScript defines the following operators (listed in order from lowest to highest precedence):

Operator	Meaning	Precedence
A = B	assignment	0
A or B	logical OR: true if either operand is true	1
A and B	logical AND: true if both operands are true	2
not A	logical negation: true if its operand is false, and vice versa	3
A isa B	type checking	4
A == B	equality comparison: true if operands are equal	5
A != B	inequality comparison: true if operands are not equal	5
A > B	greater-than comparison	5
A < B	less-than comparison	5
A >= B	greater-than or equal-to comparison	5
A <= B	less-than or equal-to comparison	5
A + B	addition or concatenation	6
A - B	subtraction or string trimming	6
A * B	multiplication or replication	7
A / B	division or reduction	7
A % B	modulo (remainder)	7
-A	unary minus (numeric negation)	8
new A	instantiation	9
@A	address-of (reference function without invoking it)	10
A ^ B	power: A raised to the power of B	11
A[B]	indexing	12
A[B:C]	slicing	12
A(B, C...)	calling a function	12
A.B	dot operator	12

Chaining Operators

Most binary operators in MiniScript can be combined into chains, for example 39 + 2 + 1. The details depend on the type of operator:

Arithmetic Operators

In an expression involving a chain of arithmetic operators, the highest-precedent operators are evaluated first, as in standard algebra. You can always use parentheses to break such a chain into smaller chunks, forcing a different evaluation order.

Code	Result
2 + 5 * 8	42
(2 + 5) * 8	56
3 ^ 2 + 4 ^ 2	25

Comparison Operators

In the case of comparison operators (==, !=, >, <, >= and <=), operands are compared in pairs from left to right. All comparisons must be true for the complete chained expression to be considered true. The most common use of this is to check whether a variable is in a certain range, with an expression like 0 < x < 10, which is true only if x is between 0 and 10 (non-inclusive).

Code	Given	Result	Read As
0 < x < 10	x = 5	true	x is between 0 and 10
0 < x < 10	x = 10	false	x is between 0 and 10
0 < x <= 10	x = 10	true	x is between 0 and 10 (including 10)
0 < x < 10 < y	x = 5; y = 15	true	x is between 0 and 10, and 10 is less than y
0 < x == 5 < y	x = 5; y = 15	true	0 < x and x == 5 and 5 < y

Dot Operator

A chain of dot operations is evaluated one step at a time left to right.

For example, given the code:

foo.bar.baz

MiniScript proceeds in the following steps:

1. foo.bar is evaluated by looking up "bar" in foo (and in the event that this references a function, it's invoked with self bound to foo.
2. .baz is evaluated by looking up "baz" in the result of step 1 (which should be a map). (And if "baz" references a function, it's invoked with self bound to the map from step 1.)

This can continue for an arbitrarily long chain of dot operators.

Math-assignment operators

In version 1.6 the math-assignment operators were added. They overwrite the value of the first operand variable with the result of the operation when performing the operator without assignment.

x = 42
x += 13  // x = x + 13
print x  // 55

s = "hello.ms"
s -= ".ms"  // s = s - ".ms"
print s  // "hello"

Operator	Meaning
A += B	A = A + B
A -= B	A = A - B
A *= B	A = A * B
A /= B	A = A / B
A %= B	A = A % B
A ^= B	A = A ^ B

Tricky spaces

MiniScript allows an expression to be the entire statement (which is useful in REPL where it evaluates the expression and immediately prints the result).

4 + 5           // REPL prints 9

f = function(x,y)
	x + y       // the result is "dropped"
end function
f 4, 5          // prints nothing

There are a few cases when using different spacing around operators in such expressions may make MiniScript confuse it with a function call:

X[Y]            // Index X with key Y
X [Y]           // Call function X with argument [Y]

X-Y             // Subtract Y from X
X- Y            // Subtract Y from X
X -Y            // Call function X with argument -Y
X - Y           // Subtract Y from X

Follow a simple convention to avoid such problems: put spaces around arithmetic operators and if possible don't use a space between an unary operator and its operand.