[ The language
defines the following six categories of operators (given in order of
increasing precedence). The corresponding operator_symbols,
and only those, can be used as designators
in declarations of functions for user-defined operators. See 6.6,
“Overloading of Operators”.]

For a sequence of operators of the same precedence
level, the operators are associated with their operands in textual order
from left to right. Parentheses can be used to impose specific associations.

See the Implementation Permissions below regarding
flexibility in reassociating operators of the same precedence.

For each
form of type definition, certain of the above operators are *predefined*;
that is, they are implicitly declared immediately after the type definition.
For
each such implicit operator declaration, the parameters are called Left
and Right for *binary* operators; the single parameter is called
Right for *unary* operators. [An expression of the form X op Y,
where op is a binary operator, is equivalent to a function_call
of the form "op"(X, Y). An expression of the form op Y, where
op is a unary operator, is equivalent to a function_call
of the form "op"(Y). The predefined operators and their effects
are described in subclauses 4.5.1 through
4.5.6.]

[ The predefined operations on
integer types either yield the mathematically correct result or raise
the exception Constraint_Error. For implementations that support the
Numerics Annex, the predefined operations on real types yield results
whose accuracy is defined in Annex G, or raise
the exception Constraint_Error. ]

The implementation of a predefined
operator that delivers a result of an integer or fixed point type may
raise Constraint_Error only if the result is outside the base range of
the result type.

The implementation of a predefined
operator that delivers a result of a floating point type may raise Constraint_Error
only if the result is outside the safe range of the result type.

For a sequence of predefined operators of the same
precedence level (and in the absence of parentheses imposing a specific
association), an implementation may impose any association of the operators
with operands so long as the result produced is an allowed result for
the left-to-right association, but ignoring the potential for failure
of language-defined checks in either the left-to-right or chosen order
of association.

Note that this permission does not apply to
user-defined operators.

NOTES

11 The two operands of an expression of
the form X op Y, where op is a binary operator, are evaluated in an arbitrary
order, as for any function_call
(see 6.4).

X > 4.0

-4.0*A**2 --* same as –(4.0 * (A**2))*

**abs**(1 + A) + B --* same as (abs (1 + A)) + B*

Y**(-3) --* parentheses are necessary*

A / B * C --* same as (A/B)*C*

A + (B + C) --* evaluate B + C before adding it to A *

Y**(-3) --

A / B * C --

A + (B + C) --

We don't give a detailed definition of precedence,
since it is all implicit in the syntax rules anyway.

The permission to reassociate is moved here
from RM83-11.6(5), so it is closer to the rules defining operator association.

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