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A1. Inform operators

In the table, "Level'' refers to precedence level: thus *, on level 6, has precedence over +, down on level 5, but both subordinate to unary -, up on level 8. The "associativity'' of an operator is the way it brackets up if the formula doesn't specify this: for instance, - is left associative because 
    a - b - c
is understood as 
    (a - b) - c
with brackets going on the left. With some Inform operators, you're not allowed to be vague like this; these are the ones whose associative is listed as "none''. Thus 
    a == b == c
will produce an error insisting that brackets be written into the program to make clear what the meaning is. Given the table (and sufficient patience) all expressions can be broken down into order: for instance 
    a * b .& c --> d / - f
is calculated as 
    ( a*((b.&c)-->d) ) / (-f)

0 , binary left separating values to work out
1 = binary right set equal to
2 && binary left logical AND
2 || binary left logical OR
2 ~~ unary (pre) logical NOT
3 == binary none equal to?
3 ~= binary none not equal to?
3 > binary none greater than?
3 >= binary none greater than or equal to?
3 < binary none less than?
3 <= binary none less than or equal to?
3 has binary none object has this attribute?
3 hasnt binary none object hasn't this attribute?
3 in binary none first obj a child of second?
3 notin binary none first obj not a child of second?
3 ofclass binary none obj inherits from class?
3 provides binary none obj provides this property?
4 or binary left separating alternative values
5 + binary left 16-bit signed addition
5 - binary left 16-bit signed subtraction
6 * binary left 16-bit signed multiplication
6 / binary left 16-bit signed integer division
6 % binary left 16-bit signed remainder
6 & binary left bitwise AND
6 | binary left bitwise OR
6 ~ unary (pre) bitwise NOT
7 -> binary left byte array entry
7 --> binary left word array entry
8 - unary (pre) 16-bit (signed!) negation
9 ++ unary (pre/post) increment
9 -- unary (pre/post) decrement
10 .& binary left property address
10 .# binary left property length
11 (...) binary left function call on right hand side
12 . binary left property value
13 :: binary left "superclass'' operator
14 (...) binary left function call on left hand side
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Mechanically translated to HTML from third edition as revised 16 May 1997. Copyright © Graham Nelson 1993, 1994, 1995, 1996, 1997: all rights reserved.