Language

Operators & Expressions

The precedence ladder, from primary expressions to conditionals

Notch parses expressions in a precedence ladder. The lower the number, the tighter the binding.

Quick reference

items[0].trim()              # index, call
-n    !ok    not ok          # unary
2 * 3 / 4 % 5                 # multiply, divide, remainder
1 + 2 - 4                    # add, subtract
2 < 3   2 <= 3   2 > 3       # comparison
1 == 1    1 != 2             # equality
'notch' starts with 'no'     # string tests
'notch' ends with 'ch'
'notch' contains 'otc'
'' is empty    [1] is not empty
true && true    done || failed   # logical (also: and / or)
x ?: 'default'               # fallback
'yes' if cond else 'no'      # conditional

Precedence table

Precedence	Operators
expr(0)	int, boolean, string, ident, parens, list, map
expr(10)	call, index
expr(20)	negate, inverse
expr(30)	multiplication, division, remainder
expr(40)	addition, subtraction
expr(50)	less, greater, lessequal, greaterequal
expr(60)	equality
expr(70)	logical and
expr(80)	logical or
expr(90)	fallback
expr(100)	conditional

String tests

Three infix tests operate on strings:

'notch' starts with 'no'
'notch' ends with 'ch'
'notch' contains 'otc'

Custom operators

Notch has three operators that are not built from a single token.

Fallback

expr ?: expr

The fallback operator evaluates the left-hand side; if the result is null or undefined, it evaluates the right-hand side.

Conditional

expr if expr [else expr]

The conditional evaluates the second expression as a predicate. If it is true, the first expression is returned. If it is false and an else branch is present, the third expression is returned. With no else branch and a false predicate, the result is undefined.

Emptiness

expr is empty
expr is not empty

Tests whether a value is empty. Empty means an empty string, an empty list, an empty map, or null. Each of these is true:

"" is empty
[1] is not empty
null is empty