Шрифт:
< <= 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.
.TS
center, box;
с s
lfCW l.
\fBTable 2:\fP Built-in Functions
.sp .5
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.
.TS
center, box;
c s s
lfCW n l.
\fBTable 3:\fP Built-in Constants
.sp .5
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
.ix [hoc] input~format
@hoc@: statements are terminated by newlines.
This causes some peculiar behavior.
The following are legal
.IT if
statements:
.DS
.ft CW
if (x < 0) print(y) else print(z)