UNIX

 | expr binop expr

 | unop expr

 | function ( arguments )

.R

.DE

Numbers are floating point.

The input format is

that recognized by @scanf@(3):

.ix [scanf]

digits, decimal point, digits,

.ix [hoc] manual

.ix assignment expression

.ix multiple assignment

@e@ or @E@, signed exponent.

At least one digit or a decimal point

must be present;

the other components are optional.

.PP

Variable names are formed from a letter

followed by a string of letters and numbers,

@binop@ refers to binary operators such

as addition or logical comparison;

@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