UNIX — универсальная среда программирования

@unop@ refers to the two negation operators,

'!' (logical negation, 'not')

and '\-' (arithmetic negation, sign change).

Table 1 lists the operators.

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\fBTable 1:\fP Operators, in decreasing order of precedence

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^       exponentiation (\s-1FORTRAN\s0 **), right associative

! \-    (unary) logical and arithmetic negation

* /     multiplication, division

+ \-    addition, subtraction

=    relational operators: greater, greater or equal,

=    less, less or equal,

\== != equal, not equal (all same precedence)

      logical AND (both operands always evaluated)

||      logical OR (both operands always evaluated)

\=     assignment, right associative

.ТЕ

.ix table~of [hoc] operators

.PP

Functions, as described later, may be defined by the user.

Function arguments are expressions separated by commas.

There are also a number of built-in functions,

all of which take a single argument,

described in Table 2.

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\fBTable 2:\fP Built-in Functions

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abs(x)   @| x |@, absolute value of @x@

atan(x)  arc tangent of @x@

cos(x)   @cos (x)@, cosine of @x@

exp(x)   @e sup x@, exponential of @x@

int(x)   integer part of @x@, truncated towards zero

log(x)   @log (x)@, logarithm base @e@ of @x@

log10(x) @log sub 10 (x)@, logarithm base 10 of @x@

sin(x)   @sin (x)@, sine of @x@

sqrt(x)  @sqrt x@, @x sup half@

.ТЕ

.ix table~of [hoc] functions

.PP

Logical expressions have value 1.0 (true) and 0.0 (false).

As in C,

any non-zero value is taken to be true.

As is always the case with floating point numbers,

equality comparisons are inherently suspect. .PP

.I Hoc

also has a few built-in constants, shown in Table 3.

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\fBTable 3:\fP Built-in Constants

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DEG   57.29577951308232087680 @180/ pi@, degrees per radian

E     2.71828182845904523536  @e@, base of natural logarithms

GAMMA 0.57721566490153286060  @gamma@, Euler-Mascheroni constant

PHI   1.61803398874989484820  @( sqrt 5 +1)/2@, the golden ratio

PI    3.14159265358979323846  @pi@, circular transcendental number

.ТЕ

.ix table~of [hoc] constants

.NH

Statements and Control Flow

.PP

.I Hoc

statements have the following grammar:

.DS

.I

stmt: expr

 | variable = expr

 | procedure ( arglist )

 | while ( expr ) stmt

 | if ( expr ) stmt

 | if ( expr ) stmt else stmt

 | { stmtlist }

 | print expr-list

 | return optional-expr

stmtlist: \fR(nothing)\fI

 | stmlist stmt

.R

.DE

An assignment is parsed by default as a statement rather than

an expression, so assignments typed interactively

do not print their value.

.PP

Note that semicolons are not special to